# Math.floor()

## BaselineWidely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

`Math.floor()` 函式會回傳小於等於所給數字的最大整數。

## 語法

```Math.floor(x)
```

`x`

## 描述

`floor()``Math`的靜態函式, 所以不需實體化`Math` 物件, 只要直接呼叫 `Math.floor()`就能使用。

(此外`Math` 並不是建構子).

## 範例

### 使用 `Math.floor()`

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

js
``````// Closure
(function () {
/**
* 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
if (!Math.round10) {
Math.round10 = function (value, exp) {
};
}
// Decimal floor
if (!Math.floor10) {
Math.floor10 = function (value, exp) {
};
}
// Decimal ceil
if (!Math.ceil10) {
Math.ceil10 = function (value, exp) {
};
}
})();

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

## 規範

Specification
ECMAScript Language Specification
# sec-math.floor

## 瀏覽器相容性

BCD tables only load in the browser