1、清除左空格/右空格

function ltrim(s){ return s.replace( /^(\s*|　*)/, ""); } 
function rtrim(s){ return s.replace( /(\s*|　*)$/, ""); }

2、判断是否以某个字符串开头

String.prototype.startWith = function (s) {
    return this.indexOf(s) == 0
}

3、判断是否以某个字符串结束

String.prototype.endWith = function (s) {
    var d = this.length - s.length;
    return (d >= 0 && this.lastIndexOf(s) == d)
}