# Math.floor()

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The `Math.floor()` function returns the largest integer less than or equal to a given number.

## Syntax

`Math.floor(x)`

`x`
A number.

### Return value

A number representing the largest integer less than or equal to the specified number.

## Description

Because `floor()` is a static method of `Math`, you always use it as `Math.floor()`, rather than as a method of a `Math` object you created (`Math` is not a constructor).

Note: `Math.floor(null)` returns 0, not a `NaN`.

## Examples

### Using `Math.floor()`

```Math.floor( 45.95); //  45
Math.floor( 45.05); //  45
Math.floor(  4   ); //   4
Math.floor(-45.05); // -46
Math.floor(-45.95); // -46
```

```/**
* Decimal adjustment of a number.
*
* @param {String}  type  The type of adjustment.
* @param {Number}  value The number.
* @param {Integer} exp   The exponent (the 10 logarithm of the adjustment base).
* @returns {Number} The adjusted value.
*/
// If the exp is undefined or zero...
if (typeof exp === 'undefined' || +exp === 0) {
return Math[type](value);
}
value = +value;
exp = +exp;
// If the value is not a number or the exp is not an integer...
if (isNaN(value) || !(typeof exp === 'number' && exp % 1 === 0)) {
return NaN;
}
// Shift
value = value.toString().split('e');
value = Math[type](+(value[0] + 'e' + (value[1] ? (+value[1] - exp) : -exp)));
// Shift back
value = value.toString().split('e');
return +(value[0] + 'e' + (value[1] ? (+value[1] + exp) : exp));
}

// Decimal round
const round10 = (value, exp) => decimalAdjust('round', value, exp);
// Decimal floor
const floor10 = (value, exp) => decimalAdjust('floor', value, exp);
// Decimal ceil
const ceil10 = (value, exp) => decimalAdjust('ceil', value, exp);

// Round
round10(55.55, -1);   // 55.6
round10(55.549, -1);  // 55.5
round10(55, 1);       // 60
round10(54.9, 1);     // 50
round10(-55.55, -1);  // -55.5
round10(-55.551, -1); // -55.6
round10(-55, 1);      // -50
round10(-55.1, 1);    // -60
// Floor
floor10(55.59, -1);   // 55.5
floor10(59, 1);       // 50
floor10(-55.51, -1);  // -55.6
floor10(-51, 1);      // -60
// Ceil
ceil10(55.51, -1);    // 55.6
ceil10(51, 1);        // 60
ceil10(-55.59, -1);   // -55.5
ceil10(-59, 1);       // -50
```

## Specifications

Specification Status Comment
ECMAScript 1st Edition (ECMA-262) Standard Initial definition. Implemented in JavaScript 1.0.
ECMAScript 5.1 (ECMA-262)
The definition of 'Math.floor' in that specification.
Standard
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Math.floor' in that specification.
Standard
ECMAScript Latest Draft (ECMA-262)
The definition of 'Math.floor' in that specification.
Draft

## Browser compatibility

Update compatibility data on GitHub
Desktop Mobile Server Chrome Edge Firefox Internet Explorer Opera Safari Android webview Chrome for Android Firefox for Android Opera for Android Chrome Full support Yes Edge Full support 12 Firefox Full support 1 IE Full support Yes Opera Full support Yes Safari Full support Yes WebView Android Full support Yes Chrome Android Full support Yes Firefox Android Full support 4 Opera Android Full support Yes Safari iOS Full support Yes Samsung Internet Android Full support Yes nodejs Full support Yes

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