JavaScript十大取整方法实例教程

// js内置函数，注意接受参数是string，所以调用该方法时存在类型转换
parseInt("1.5555") // => 1

// 注意toFixed返回的字符串，若想获得整数还需要做类型转换
1.5555.toFixed(0) // => "1"

// 向上取整
Math.ceil(1.5555) // => 2

// 向下取整
Math.floor(1.5555) // => 1

// 四舍五入取整
Math.round(1.5555) // => 2

Math.round(1.4999) // => 1

// 舍弃小数取整
Math.trunc(1.5555) // => 1

// 利用位运算取整，仅支持32位有符号整型数，小数位会舍弃，下同
~~1.5555 // => 1

1.5555 | 0 // => 1

1.5555^0 // => 1

1.5555<<0 // => 1

darwin x64
整数取整#getNum1#parseInt x 210,252,532 ops/sec ±2.74% (85 runs sampled)
整数取整#getNum2#toFixed x 3,281,188 ops/sec ±1.54% (86 runs sampled)
整数取整#getNum3#Math.ceil x 778,272,700 ops/sec ±3.97% (87 runs sampled)
整数取整#getNum4#Math.floor x 816,990,140 ops/sec ±0.54% (88 runs sampled)
整数取整#getNum5#Math.round x 814,868,414 ops/sec ±0.65% (88 runs sampled)
整数取整#getNum6#Math.trunc x 821,032,596 ops/sec ±0.54% (91 runs sampled)
整数取整#getNum7#~~num x 813,589,741 ops/sec ±0.67% (90 runs sampled)
整数取整#getNum8#num | 0 x 815,070,107 ops/sec ±0.65% (90 runs sampled)
整数取整#getNum9#num ^ 0 x 812,635,464 ops/sec ±0.74% (90 runs sampled)
整数取整#getNum10#num << 0 x 819,230,753 ops/sec ±0.49% (91 runs sampled)
Fastest is 整数取整#getNum6#Math.trunc,整数取整#getNum10#num << 0