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+---
+title: Solve common problems in your JavaScript code
+slug: Learn/JavaScript/Howto
+tags:
+  - 자바스크립트
+  - 초보자
+  - 학습
+translation_of: Learn/JavaScript/Howto
+---
+<div>{{LearnSidebar}}</div>
+
+<div>다음의 링크들은 당신의 자바스크립트 코드가 정상적으로 작동할 수 있게 고쳐야되는 흔한 문제들의 해결책을 제시한다.</div>
+
+<h2 id="초보자들의_흔한_실수들">초보자들의 흔한 실수들</h2>
+
+<h3 id="스펠링과_대소문자를_제대로_해라">스펠링과 대소문자를 제대로 해라</h3>
+
+<p>코드가 작동하지 않거나 브라우저가 무언가가 undefined라고 불평하면 모든 변수 이름, 함수 이름 등을 정확하게 입력했는지 확인하십시오. </p>
+
+<p>문제를 일으키는 몇 가지 일반적인 내장 브라우저 함수는 다음과 같습니다.</p>
+
+<table class="standard-table">
+ <thead>
+  <tr>
+   <th scope="col">올바른</th>
+   <th scope="col">잘못된</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="세미콜론의_위치">세미콜론의 위치</h3>
+
+<p>세미콜론의 위치가 잘못 되지 않았는지 확인하세요. 예를들어:</p>
+
+<table class="standard-table">
+ <thead>
+  <tr>
+   <th scope="col">올바른</th>
+   <th scope="col">잘못된</th>
+  </tr>
+  <tr>
+   <td><code>elem.style.color = 'red';</code></td>
+   <td><code>elem.style.color = 'red;'</code></td>
+  </tr>
+ </thead>
+</table>
+
+<h3 id="함수">함수</h3>
+
+<p>함수와 관련하여 실수할 수 있는 것들이 많이 있습니다.</p>
+
+<p>가장 흔한 실수는 함수를 선언하고 어디서도 호출하지 않는 것입니다. 예를 들어:</p>
+
+<pre class="brush: js">function myFunction() {
+  alert('This is my function.');
+};</pre>
+
+<p>위 코드는 호출하지 않는 이상 아무것도 하지 않습니다.</p>
+
+<pre class="brush: js">myFunction();</pre>
+
+<h4 id="함수_스코프">함수 스코프</h4>
+
+<p><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions#Function_scope_and_conflicts">함수는 각자의 스코프가 있음</a>을 명심하세요 — 변수를 전역으로 선언하거나 함수에서 <a href="/en-US/docs/Learn/JavaScript/Building_blocks/Return_values">값을 리턴</a>하지 않는한 함수 밖에서 함수 내부에 설정된 변수 값에 접근 할 수 없습니다. (즉, 어떠한 함수 내에서도 접근 안됨)</p>
+
+<h4 id="리턴_문_이후_코드_실행">리턴 문 이후 코드 실행</h4>
+
+<p>함수 밖으로 값을 리턴할 때, 자바스크립트 인터프리터가 함수를 완전히 빠져나감을 명심하세요.  — 리턴 문 이후에 선언된 코드는 절대로 실행되지 않습니다.</p>
+
+<p>사실, 몇몇 브라우저들은 (파이어폭스 처럼) 리턴 문 이후에 코드가 있다면 개발자 콘솔에 에러 메세지를 줍니다. 파이어폭스는 "unreachable code after return statement" 라고 알려줍니다.</p>
+
+<h3 id="오브젝트_표기_vs_일반적_할당">오브젝트 표기 vs 일반적 할당</h3>
+
+<p>보통 자바스크립테어서 무언가를 할당하려고 할때, 단일 등호기호를 사용합니다. 예:</p>
+
+<pre class="brush: js">const myNumber = 0;</pre>
+
+<p>하지만, 이 방법은 <a href="/en-US/docs/Learn/JavaScript/Objects">오브젝트</a>에선 동작하지 않습니다. — 오브젝트에선 멤버와 값 사이를 콜론으로 구분하고, 각 멤버들은 콤마로 구분합니다, 예를 들어:</p>
+
+<pre class="brush: js">const myObject = {
+  name: 'Chris',
+  age: 38
+}</pre>
+
+<h2 id="기본_정의">기본 정의</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">자바스크립트란 무엇인가?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Variables#What_is_a_variable">변수는 무엇인가?</a> </li>
+ <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Strings">문자열은 무엇인가?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Arrays#What_is_an_Array">배열은 무엇인가?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Looping_code">루프는 무엇인가?</a></li>
+</ul>
+</div>
+
+<div class="column-half">
+<ul>
+ <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Functions">함수는 무엇인가?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events">What is an event?</a> <a href="/en-US/docs/Learn/JavaScript/Building_blocks/Events">이벤트는 무엇인가?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/Objects/Basics#Object_basics">오브젝트는 무엇인가?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/Objects/JSON#No_really_what_is_JSON">JSON은 무엇인가?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Introduction#What_are_APIs">web API는 무엇인가?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Manipulating_documents#The_document_object_model">DOM은 무엇인가?</a></li>
+</ul>
+</div>
+</div>
+
+<h2 id="Basic_use_cases">Basic use cases</h2>
+
+<div class="column-container">
+<div class="column-half">
+<h3 id="General">General</h3>
+
+<ul>
+ <li><a href="/en-US/docs/Learn/JavaScript/First_steps/What_is_JavaScript#How_do_you_add_JavaScript_to_your_page">How do you add JavaScript to your page?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/First_steps/What_is_JavaScript#Comments">How do you add comments to JavaScript code?</a></li>
+</ul>
+
+<h3 id="Variables">Variables</h3>
+
+<ul>
+ <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Variables#Declaring_a_variable">How do you declare a variable?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Variables#Initializing_a_variable">How do you initialize a variable with a value?</a></li>
+ <li><a href="https://developer.mozilla.org/en-US/docs/Learn/JavaScript/First_steps/Variables#Updating_a_variable">How do you update a variable's value?</a> (also see <a href="/en-US/docs/Learn/JavaScript/First_steps/Math#Assignment_operators">Assignment operators</a>)</li>
+ <li><a href="https://developer.mozilla.org/en-US/docs/Learn/JavaScript/First_steps/Variables#Variable_types">What data types can values have in JavaScript?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Variables#Loose_typing">What does 'loosely typed' mean?</a></li>
+</ul>
+
+<h3 id="Math">Math</h3>
+
+<ul>
+ <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Math#Types_of_numbers">What types of number do you have to deal with in web development?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Math#Arithmetic_operators">How do you do basic math in JavaScript?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Math#Operator_precedence">What is operator precedence, and how is it handled in JavaScript?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Math#Increment_and_decrement_operators">How do you increment and decrement values in JavaScript?</a></li>
+ <li><a href="https://developer.mozilla.org/en-US/docs/Learn/JavaScript/First_steps/Math#Comparison_operators">How do you compare values in JavaScript?</a> (e.g. to see which one is bigger, or to see if one value is equal to another).</li>
+</ul>
+
+<h3 id="Strings">Strings</h3>
+
+<ul>
+ <li><a href="/en-US/docs/Learn/JavaScript/First_steps/Strings#Creating_a_string">How do you create a string in 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="Events">Events</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="Object-oriented_JavaScript">Object-oriented JavaScript</h3>
+
+<ul>
+ <li><a href="/en-US/docs/Learn/JavaScript/Objects/Object_prototypes">What are object prototypes?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/Objects/Object_prototypes#The_constructor_property">What is the constructor property, and how can you use it?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/Objects/Object_prototypes#Modifying_prototypes">How do you add methods to the constructor?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/Objects/Inheritance">How do you create a new constructor that inherits its members from a parent constructor?</a></li>
+ <li><a href="/en-US/docs/Learn/JavaScript/Objects/Inheritance#Object_member_summary">When should you use inheritance in 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">How do you manipulate the DOM (e.g. adding or removing elements) using JavaScript?</a></li>
+</ul>
+
+<p> </p>
+</div>
+</div>