[JavaScript]OO编程之自定义方法

范例一：

String.prototype.startWith=function(str){if(str==null||str==""||this.length==0||str.length>this.length)  return false;if(this.substr(0,str.length)==str)  return true;else  return false;return true;};

用法："how are you".startWith("how");

范例二：

取两个数组的差集

Array.prototype.desc = function(small) {  var result = new Array();

  // 判断small是不是数组  if(Object.prototype.toString.apply(small) === '[object Array]'){    var big = this;    for (var i = 0; i < big.length; i++) {      if (!small.contains(big[i])) {        result.push(big[i]);      }    }  }  return result;};

判断元素在数组中是否存在Array.prototype.contains = function(o) {  var flag = false;  for ( var i = 0; i < this.length; i++) {    if (o == this[i]) {      flag = true;      break;    }  }  return flag;};