--- title: 'RangeError: precision is out of range' slug: Web/JavaScript/Reference/Errors/Precision_range tags: - JavaScript - 范围错误 - 错误 translation_of: Web/JavaScript/Reference/Errors/Precision_range --- <div>{{jsSidebar("Errors")}}</div> <h2 id="描述">描述</h2> <pre class="syntaxbox">RangeError: precision {0} out of range (Firefox) RangeError: toExponential() argument must be between 0 and 20 (Chrome) RangeError: toFixed() digits argument must be between 0 and 20 (Chrome) RangeError: toPrecision() argument must be between 1 and 21 (Chrome) </pre> <h2 id="错误类型">错误类型</h2> <p>{{jsxref("RangeError")}}</p> <h2 id="什么地方出错了?">什么地方出错了?</h2> <p>以下的某个方法传入了一个超出精度范围的参数:</p> <ul> <li>{{jsxref("Number.prototype.toExponential()")}}</li> <li>{{jsxref("Number.prototype.toFixed()")}}</li> <li>{{jsxref("Number.prototype.toPrecision()")}}</li> </ul> <p>通常这些方法允许的参数范围介于0和20(或21)之间。需要注意的是,ECMAScript标准是允许扩展这个范围的。</p> <table class="standard-table"> <thead> <tr> <th scope="col">Method</th> <th scope="col">Firefox (SpiderMonkey)</th> <th scope="col">Chrome, Opera (V8)</th> </tr> </thead> <tbody> <tr> <td>{{jsxref("Number.prototype.toExponential()")}}</td> <td>0 to 100</td> <td>0 to 20</td> </tr> <tr> <td>{{jsxref("Number.prototype.toFixed()")}}</td> <td>-20 to 100</td> <td>0 to 20</td> </tr> <tr> <td>{{jsxref("Number.prototype.toPrecision()")}}</td> <td>1 to 100</td> <td>1 to 21</td> </tr> </tbody> </table> <h2 id="示例">示例</h2> <h3 id="错误的示例">错误的示例</h3> <pre class="brush: js example-bad">77.1234.toExponential(-1); // RangeError 77.1234.toExponential(101); // RangeError 2.34.toFixed(-100); // RangeError 2.34.toFixed(1001); // RangeError 1234.5.toPrecision(-1); // RangeError 1234.5.toPrecision(101); // RangeError </pre> <h3 id="正确的示例">正确的示例</h3> <pre class="brush: js example-good">77.1234.toExponential(4); // 7.7123e+1 77.1234.toExponential(2); // 7.71e+1 2.34.toFixed(1); // 2.3 2.35.toFixed(1); // 2.4 (note that it rounds up in this case) 5.123456.toPrecision(5); // 5.1235 5.123456.toPrecision(2); // 5.1 5.123456.toPrecision(1); // 5 </pre> <h2 id="相关页面">相关页面</h2> <ul> <li>{{jsxref("Number.prototype.toExponential()")}}</li> <li>{{jsxref("Number.prototype.toFixed()")}}</li> <li>{{jsxref("Number.prototype.toPrecision()")}}</li> </ul>