Revision 1089335 of Number.prototype.toExponential()

<div>{{JSRef}}</div>

<p>The <strong><code>toExponential()</code></strong> method returns a string representing the Number object in exponential notation.</p>

<h2 id="Syntax">Syntax</h2>

<pre class="syntaxbox">
<code><var>numObj</var>.toExponential([<var>fractionDigits</var>])</code></pre>

<h3 id="Parameters">Parameters</h3>

<dl>
 <dt><code>fractionDigits</code></dt>
 <dd>Optional. An integer specifying the number of digits after the decimal point. Defaults to as many digits as necessary to specify the number.</dd>
</dl>

<h3 id="Returns">Returns</h3>

<p>A string representing a {{jsxref("Number")}} object in exponential notation with one digit before the decimal point, rounded to <code>fractionDigits</code> digits after the decimal point. If the <code>fractionDigits</code> argument is omitted, the number of digits after the decimal point defaults to the number of digits necessary to represent the value uniquely.</p>

<p>If you use the <code>toExponential()</code> method for a numeric literal and the numeric literal has no exponent and no decimal point, leave whitespace(s) before the dot that precedes the method call to prevent the dot from being interpreted as a decimal point.</p>

<p>If a number has more digits than requested by the <code>fractionDigits</code> parameter, the number is rounded to the nearest number represented by <code>fractionDigits</code> digits. See the discussion of rounding in the description of the {{jsxref("Number.prototype.toFixed", "toFixed()")}} method, which also applies to <code>toExponential()</code>.</p>

<h3 id="Throws">Throws</h3>

<dl>
 <dt>{{jsxref("RangeError")}}</dt>
 <dd>If <code>fractionDigits</code> is too small or too large. Values between 0 and 20, inclusive, will not cause a {{jsxref("RangeError")}}. Implementations are allowed to support larger and smaller values as well.</dd>
 <dt>{{jsxref("TypeError")}}</dt>
 <dd>If this method is invoked on an object that is not a {{jsxref("Number")}}.</dd>
</dl>

<h2 id="Examples">Examples</h2>

<h3 id="Using_toExponential">Using <code>toExponential</code></h3>

<pre class="brush: js">
var numObj = 77.1234;

console.log(numObj.toExponential());  // logs 7.71234e+1
console.log(numObj.toExponential(4)); // logs 7.7123e+1
console.log(numObj.toExponential(2)); // logs 7.71e+1
console.log(77.1234.toExponential()); // logs 7.71234e+1
console.log(77 .toExponential());     // logs 7.7e+1
</pre>

<h2 id="Specifications">Specifications</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
  <tr>
   <td>{{SpecName('ES3')}}</td>
   <td>{{Spec2('ES3')}}</td>
   <td>Initial definition. Implemented in JavaScript 1.5.</td>
  </tr>
  <tr>
   <td>{{SpecName('ES5.1', '#sec-15.7.4.6', 'Number.prototype.toExponential')}}</td>
   <td>{{Spec2('ES5.1')}}</td>
   <td>&nbsp;</td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-number.prototype.toexponential', 'Number.prototype.toExponential')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td>&nbsp;</td>
  </tr>
  <tr>
   <td>{{SpecName('ESDraft', '#sec-number.prototype.toexponential', 'Number.prototype.toExponential')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td>&nbsp;</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility">Browser compatibility</h2>

<div>{{CompatibilityTable}}</div>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Chrome for Android</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<h2 id="See_also">See also</h2>

<ul>
 <li>{{jsxref("Number.prototype.toFixed()")}}</li>
 <li>{{jsxref("Number.prototype.toPrecision()")}}</li>
 <li>{{jsxref("Number.prototype.toString()")}}</li>
</ul>