JavaScript 去除字符串首尾空格

function trim(string) {
    if(string.trim) {
        return string.trim();
    }else {
        let reg = /^\s+|\s+$/g;
        return string.replace(reg,"");
    }
}

if(typeof String.prototype.trim !== "function") {
    let reg = /^\s+|\s+$/g;
    String.prototype.trim = function() {
        // 给原型扩展方法
        return this.replace(reg, "");
    }
}