path: root/files/pt-br/aprender/javascript/howto/index.html

---
title: Solve common problems in your JavaScript code
slug: Aprender/JavaScript/Howto
translation_of: Learn/JavaScript/Howto
---
<div>{{LearnSidebar}}</div>

<p class="summary">Os links a seguir apontam soluções para problemas comuns do dia a dia, você precisará consertar em ordem para que seu código javascript execute corretamente.</p>

<h2 id="Erros_comuns_de_iniciantes">Erros comuns de iniciantes</h2>

<h3 id="Digitação_correta_and_casing">Digitação correta and casing</h3>

<p>Se o seu código não funciona e/ou se seu navegador indicar que algo está indefinido, verifique se você declarou todas os nomes de suas variáveis, nomes de funções, etc. corretamente.</p>

<p>Algumas funções comuns dos navegadores que causam problema são:</p>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Correto</th>
   <th scope="col">Incorreto</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td><code>getElementsByTagName()</code></td>
   <td><code>getElementbyTagName()</code></td>
  </tr>
  <tr>
   <td><code>getElementsByName()</code></td>
   <td><code>getElementByName()</code></td>
  </tr>
  <tr>
   <td><code>getElementsByClassName()</code></td>
   <td><code>getElementByClassName()</code></td>
  </tr>
  <tr>
   <td><code>getElementById()</code></td>
   <td><code>getElementsById()</code></td>
  </tr>
 </tbody>
</table>

<h3 id="Posições_de_ponto_e_vírgula">Posições de ponto e vírgula</h3>

<p>Você precisa ter certeza que você não colocou nenhum ponto e vírgula incorretamente. Por exemplo:</p>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Correct</th>
   <th scope="col">Wrong</th>
  </tr>
  <tr>
   <td><code>elem.style.color = 'red';</code></td>
   <td><code>elem.style.color = 'red;'</code></td>
  </tr>
 </thead>
</table>

<h3 id="Funções">Funções</h3>

<p>Há uma série de coisas que podem dar errado com funções</p>

<p>Um dos erros mais comuns é declarar a função, mas não chama-la em lugar nenhum. Por exemplo:</p>

<pre class="brush: js">function myFunction() {
  alert('This is my function.');
};</pre>

<p>Este código não fará nada a menos que você o chame, por exemplo com</p>

<pre class="brush: js">myFunction();</pre>

<h4 id="Escopo_da_função">Escopo da função</h4>

<p>Lembre-se que <a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions#Function_scope_and_conflicts">funções tem seu próprio escopo</a> — você não pode acessar um conjunto de valores de variáveis ​​dentro de uma função fora da função, a não ser que você tenha declarado a variável globalmente (i.e. não dentro de nenhuma função), ou retorne o valor or <a href="/en-US/docs/Learn/JavaScript/Building_blocks/Return_values">retorne o valor</a> fora da função</p>

<h4 id="Executar_o_código_antes_de_uma_declaração_de_retorno">Executar o código antes de uma declaração de retorno</h4>

<p>Remember also that when you return a value out of a function, the JavaScript interpreter exits the function — no code declared after the return statement will run.</p>

<p>In fact, some browsers (like Firefox) will give you an error message in the developer console if you have code after a return statement. Firefox gives you "unreachable code after return statement".</p>

<h3 id="Object_notation_versus_normal_assignment">Object notation versus normal assignment</h3>

<p>When you assign something normally in JavaScript, you use a single equals sign, e.g.:</p>

<pre class="brush: js">var myNumber = 0;</pre>

<p>This doesn't work in <a href="/en-US/docs/Learn/JavaScript/Objects">Objects</a>, however — with objects you need to separate member names from their values using colons, and separate each member with a comma, for example:</p>

<pre class="brush: js">var myObject = {
  name : 'Chris',
  age : 38
}</pre>

<h2 id="Definições_básicas">Definições básicas</h2>

<div class="column-container">
<div class="column-half">
<ul>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/What_is_JavaScript#A_high-level_definition">O que é Javascript?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Variables#What_is_a_variable">O que é uma variável?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Strings">O que são strings?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Arrays#What_is_an_Array">O que é um vetor?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code">O que é um laço?</a></li>
</ul>
</div>

<div class="column-half">
<ul>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions">O que é uma função?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events">O que é um evento?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Objects/Basics#Object_basics">O que é um objeto?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Objects/JSON#No_really_what_is_JSON">O que é JSON?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Introduction#What_are_APIs">O que é uma web API?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Manipulating_documents#The_document_object_model">O que é o DOM?</a></li>
</ul>
</div>
</div>

<h2 id="Casos_de_uso_básicos">Casos de uso básicos</h2>

<div class="column-container">
<div class="column-half">
<h3 id="Geral">Geral</h3>

<ul>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/What_is_JavaScript#How_do_you_add_JavaScript_to_your_page">Como adicionar JavasScript para sua página?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/What_is_JavaScript#Comments">Como adicionar comentários em um código Javascript?</a></li>
</ul>

<h3 id="Variáveis">Variáveis</h3>

<ul>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Variables#Declaring_a_variable">Como você declara uma variável?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Variables#Initializing_a_variable">Como você inicializa uma variável com um valor?</a></li>
 <li><a href="https://developer.mozilla.org/en-US/docs/Learn/JavaScript/First_steps/Variables#Updating_a_variable">Como você atualiza o valor de uma variável</a> (ver também <a href="/en-US/docs/Learn/JavaScript/First_steps/Math#Assignment_operators">Operadores de atribuição</a>)</li>
 <li><a href="https://developer.mozilla.org/en-US/docs/Learn/JavaScript/First_steps/Variables#Variable_types">Quais tipos de dados os valores podem ter em JavaScript?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Variables#Loose_typing">O que 'fracamente tipada' significa?</a></li>
</ul>

<h3 id="Matemática">Matemática</h3>

<ul>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Math#Types_of_numbers">Quais tipos de números você tem que lidar no desenvolvimento web?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Math#Arithmetic_operators">Como você faz matemática básica em JavaScript?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Math#Operator_precedence">Qual a precedência do operador, e como isso é tratado em JavaScript?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Math#Increment_and_decrement_operators">Como você incrementa e decrementa valores em JavaScript?</a></li>
 <li><a href="https://developer.mozilla.org/en-US/docs/Learn/JavaScript/First_steps/Math#Comparison_operators">Como você compara valores em JavaScript?</a> (por exemplo, para ver qual é o maior, ou para ver se um valor é igual ao outro).</li>
</ul>

<h3 id="Strings">Strings</h3>

<ul>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Strings#Creating_a_string">Como você cria uma string em JavaScript?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Strings#Single_quotes_versus_double_quotes">Do you have to use single quotes or double quotes?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Strings#Escaping_characters_in_a_string">How do you escape characters in strings?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Strings#Concatenating_strings">How do you join strings together?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Strings#Numbers_versus_strings">Can you join strings and numbers together?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods#Finding_the_length_of_a_string">How do you find the length of a string?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods#Retrieving_a_specific_string_character">How you find what character is at a certain position in a string?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods#Finding_a_substring_inside_a_string_and_extracting_it">How do you find and extract a specific substring from a string?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods#Changing_case">How do you change the case of a string?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Useful_string_methods#Updating_parts_of_a_string">How do you replace one specific substring with another?</a></li>
</ul>
</div>

<div class="column-half">
<h3 id="Arrays">Arrays</h3>

<ul>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Arrays#Creating_an_array">How do you create an array?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Arrays#Accessing_and_modifying_array_items">How do you access and modify the items in an array?</a> (this includes multidimensional arrays)</li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Arrays#Finding_the_length_of_an_array">How do you find the length of an array?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Arrays#Adding_and_removing_array_items">How you add and remove array items?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Arrays#Converting_between_strings_and_arrays">How do you split a string into array items, or join array items into a string?</a></li>
</ul>

<h3 id="Debugging_JavaScript">Debugging JavaScript</h3>

<ul>
 <li><a href="/en-US/docs/Learn/JavaScript/First_steps/What_went_wrong#Types_of_error">What are the basic types of error?</a></li>
 <li><a href="/en-US/docs/Learn/Common_questions/What_are_browser_developer_tools">What are browser developer tools, and how do you access them?</a></li>
 <li><a href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/JavaScript#The_Console_API">How do you log a value to the JavaScript console?</a></li>
 <li><a href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/JavaScript#Using_the_JavaScript_debugger">How do you use breakpoints, and other JavaScript debugging features?</a></li>
</ul>

<p>For more information on JavaScript debugging, see <a href="/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/JavaScript">Handling common JavaScript problems</a>; also see <a href="/en-US/docs/Learn/JavaScript/First_steps/What_went_wrong#Other_common_errors">Other common errors</a> for a description of common errors.</p>

<h3 id="Making_decisions_in_code">Making decisions in code</h3>

<ul>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/conditionals">How do you execute different blocks of code, depending on a variable's value or other condition?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/conditionals#if_..._else_statements">How do you use if ...else statements?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/conditionals#Nesting_if_..._else">How do nest one decision block inside another?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/conditionals#Logical_operators_AND_OR_and_NOT">How do you use AND, OR, and NOT operators in JavaScript?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/conditionals#switch_statements">How do you conveniently handle a large number of choices for one condition?</a></li>
 <li><a href="https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Building_blocks/conditionals#Ternary_operator">How do you use a ternary operator to make a quick choice between two options based on a true or false test?</a></li>
</ul>

<h3 id="Loopingiteration">Looping/iteration</h3>

<ul>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code">How do you run the same bit of code over and over again?</a></li>
 <li><a href="https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code#Exiting_loops_with_break">How do you exit a loop before the end if a certain condition is met?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code#Skipping_iterations_with_continue">How do you skip to the next iteration of a loop if a certain condition is met?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code#while_and_do_..._while">How do you use while and do ... while loops?</a></li>
 <li>How to iterate over the elements in an array</li>
 <li>How to iterate over the elements in a multidimensional array</li>
 <li>How to iterate over the members in an object</li>
 <li>How to iterate over the members of an object nested inside an array</li>
</ul>
</div>
</div>

<h2 id="Intermediate_use_cases">Intermediate use cases</h2>

<div class="column-container">
<div class="column-half">
<h3 id="Functions">Functions</h3>

<ul>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions#Built-in_browser_functions">How do you find functions in the browser?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions#Functions_versus_methods">What is the difference between a function and a method?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Build_your_own_function">How do you create your own functions?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions#Invoking_functions">How do you run (call, or invoke) a function?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions#Anonymous_functions">What is an anonymous function?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions#Function_parameters">How do you specify parameters (or arguments) when invoking a function?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions#Function_scope_and_conflicts">What is function scope?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Return_values">What are return values, and how do you use them?</a></li>
</ul>

<h3 id="Objects">Objects</h3>

<ul>
 <li><a href="/en-US/docs/Learn/JavaScript/Objects/Basics#Object_basics">How do you create an object?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Objects/Basics#Dot_notation">What is dot notation?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Objects/Basics#Bracket_notation">What is bracket notation?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Objects/Basics#Setting_object_members">How do you get and set the methods and properties of an object?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Objects/Basics#What_is_this">What is <code>this</code>, in the context of an object?</a></li>
 <li><a href="/docs/Learn/JavaScript/Objects/Object-oriented_JS#Object-oriented_programming_from_10000_meters">What is object-oriented programming?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Objects/Object-oriented_JS#Constructors_and_object_instances">What are constructors and instances, and how do you create them?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Objects/Object-oriented_JS#Other_ways_to_create_object_instances">What different ways are there to create objects in JavaScript?</a></li>
</ul>

<h3 id="JSON">JSON</h3>

<ul>
 <li><a href="/en-US/docs/Learn/JavaScript/Objects/JSON#JSON_structure">How do you structure JSON data, and read it from JavaScript?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Objects/JSON#Loading_our_JSON">How can you load a JSON file into a page?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Objects/JSON#Converting_between_objects_and_text">How do you convert a JSON object to a text string, and back again?</a></li>
</ul>
</div>

<div class="column-half">
<h3 id="Eventos">Eventos</h3>

<ul>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events#Event_handler_properties">What are event handlers and how do you use them?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events#Inline_event_handlers_%E2%80%94_don%27t_use_these">What are inline event handlers?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events#addEventListener()_and_removeEventListener()">What does the <code>addEventListener()</code> function do, and how do you use it?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events#What_mechanism_should_I_use">Which mechanism should I use to add event code to my web pages?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events#Event_objects">What are event objects, and how do you use them?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events#Preventing_default_behaviour">How do you prevent default event behaviour?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events#Event_bubbling_and_capture">How do events fire on nested elements? (event propagation, also related — event bubbling and capturing)</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events#Event_delegation">What is event delegation, and how does it work?</a></li>
</ul>

<h3 id="Javascript_Orientado_a_objetos">Javascript Orientado a objetos</h3>

<ul>
 <li><a href="/en-US/docs/Learn/JavaScript/Objects/Object_prototypes"> Quais são protótipos de objetos?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Objects/Object_prototypes#The_constructor_property">Qual é a propriedade do construtor, e como você pode usa-la?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Objects/Object_prototypes#Modifying_prototypes">Como você adiciona métodos para o construtor?</a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Objects/Inheritance">Como você cria um novo constructor que herda os membros do construtor pai? </a></li>
 <li><a href="/en-US/docs/Learn/JavaScript/Objects/Inheritance#Object_member_summary">Quando você deve usar herança em Javascript?</a></li>
</ul>

<h3 id="Web_APIs">Web APIs</h3>

<ul>
 <li><a href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Manipulating_documents#Active_learning_Basic_DOM_manipulation">Como você manipula o DOM (por exemplo, adicionando e removendo elementos) usando Javascript?</a></li>
</ul>

<p> </p>
</div>
</div>