toFixed()方法采用1 个参数，即精确的小数位数。
let num = 12.345678; // default toFixed() method
console.log(num.toFixed()); // 12
逗号分隔的内置方法
这些格式可以通过使用toLocaleString()方法来实现。
let num = 7323452568.283;
// US system en-US
console.log(num.toLocaleString('en-US')); // 7,323,452,568.283
// India system hi-IN
console.log(num.toLocaleString('hi-IN')); // 7,32,34,52,568.283
逗号分隔的自定义函数
function separateComma(val) {
// remove sign if negative
var sign = 1;
if (val < 0) {
sign = -1;
val = -val;
}
// trim the number decimal point if it exists
let num = val.toString().includes('.') ? val.toString().split('.')[0] : val.toString();
let len = num.toString().length;
let result = '';
let count = 1;
for (let i = len - 1; i >= 0; i--) {
result = num.toString()[i] + result;
if (count % 3 === 0 && count !== 0 && i !== 0) {
result = ',' + result;
}
count++;
}
// add number after decimal point
if (val.toString().includes('.')) {
result = result + '.' + val.toString().split('.')[1];
}
// return result with - sign if negative
return sign < 0 ? '-' + result : result;
}
let num1 = 12345678;
console.log(separateComma(num1));
// decimal number
let num2 = -723694769.2343;
console.log(separateComma(num2));
正则
function commaSeparateNumber(val) {
// remove sign if negative
var sign = 1;
if (val < 0) {
sign = -1;
val = -val;
}
// trim the number decimal point if it exists
let num = val.toString().includes('.') ? val.toString().split('.')[0] : val.toString();
while (/(\d+)(\d{3})/.test(num.toString())) {
// insert comma to 4th last position to the match number
num = num.toString().replace(/(\d+)(\d{3})/, '$1' + ',' + '$2');
}
// add number after decimal point
if (val.toString().includes('.')) {
num = num + '.' + val.toString().split('.')[1];
}
// return result with - sign if negative
return sign < 0 ? '-' + num : num;
}
// decimal number
let num1 = 77799;
console.log(commaSeparateNumber(num1));
// decimal number
let num2 = -72364769.1234;
console.log(commaSeparateNumber(num2));