如何舍入浮点数？

Question

JavaScript 中是否有一些有用的函数可以帮助将任何浮点数舍入到最近的邻居，无论是整数还是带有 .5 的浮点数？Input -> Output:  - > 2.1 -> 2.0   > 2.4 -> 2.5   > 1.9 -> 2....javascript

Answer 1

您可以使用以下功能：

var intvalue = Math.floor( floatvalue );

var intvalue = Math.ceil( floatvalue ); 

var intvalue = Math.round( floatvalue );

// `Math.trunc` was added in ECMAScript 6

var intvalue = Math.trunc( floatvalue );

Answer 2

不是最短但工作

function roundNumberWith05 (num){

  const diff = num - Math.floor(num);

  if (diff < 0.25 || diff > 0.75) {

    return Math.round(num * 2) / 2;

  } else {

    return num - diff + 0.5;

  }

}

console.log('2.1 --', roundNumberWith05(2.1));

console.log('2.4 --', roundNumberWith05(2.4));

console.log('1.9 --', roundNumberWith05(1.9)); 

console.log('1.75 --', roundNumberWith05(1.75)); 

console.log('1.74 --', roundNumberWith05(1.74)); 

console.log('1.76 --', roundNumberWith05(1.76)); 

console.log('2.688 --', roundNumberWith05(2.688)); 

console.log('2.2588 --', roundNumberWith05(2.2488)); 

Answer 3

尝试这个，

function my_round(x){

  return Math.floor(x) + Math.round((x - Math.floor(x)) * 2) / 2 

}

或者更好的是，使用@ritaj 建议的方法

function myRound(x){

  return Math.round(x * 2)/2 

}