js常用工具方法集合

如何将浮点数点左边的数每三位添加一个逗号，如12000000.11转化为『12,000,000.11』?

function formatNumber(value) {
var re = /^(\-?)(\d{1,3}(,\d\d\d)*(\.\d+)?|\d+(\.\d+)?)$/;
if (!re.test(value)) {
return value;
}
value += '';
const list = value.split('.');
const prefix = list[0].charAt(0) === '-' ? '-' : '';
let num = prefix ? list[0].slice(1) : list[0];
let result = '';
while (num.length > 3) {
result = `,${num.slice(-3)}${result}`;
num = num.slice(0, num.length - 3);
}
if (num) {
result = num + result;
}
return `${prefix}${result}${list[1] ? `.${list[1]}` : ''}`;
}

2.移除千分位。如『12,000,000.11』转化为 12000000.11

function removalThousandths(num)
{
var re = /^(\-?)(\d{1,3}(,\d\d\d)*(\.\d+)?|\d+(\.\d+)?)$/;
if (!re.test(num)) {
return num;
}
var x = num.toString().split(',');
return parseFloat(x.join(""));
}

获取地址栏上携带的参数，如http://www.baidu.com?test=shuju;

function getUrlParam(name) {
if (window.location.href.indexOf('?') >= 0) {
var a = window.location.href.slice(window.location.href.indexOf('?') + 1).split('&');
var t;
var i = 0;
var l = a.length;
for (; i < l; i++) {
if ((t = a[i].split('='))[0] === name) return t[1];
}
}
return null;
}

getUrlParam('test'); // 得到shuju

4.获取文件后缀

function getFileExtension(filename) {
return filename.slice((filename.lastIndexOf(".") - 1 >>> 0) + 2);
}