in_array function implemented in JavaScript_javascript skills
In JS, there is no function that can be used directly to determine whether a value is in an array. For example, there is the in_array() function in PHP. But we can write a function like in_array() to determine whether a value is in the function.
/** * JS判断一个值是否存在数组中 */ // 定义一个判断函数 var in_array = function(arr){ // 判断参数是不是数组 var isArr = arr && console.log( typeof arr==='object' ? arr.constructor===Array ? arr.length ? arr.length===1 ? arr[0]:arr.join(','):'an empty array': arr.constructor: typeof arr ); // 不是数组则抛出异常 if(!isArr){ throw "arguments is not Array"; } // 遍历是否在数组中 for(var i=0,k=arr.length;i<k;i++){ if(this==arr[i]){ return true; } } // 如果不在数组中就会返回false return false; } // 给字符串添加原型 String.prototype.in_array = in_array; // 给数字类型添加原型 Number.prototype.in_array = in_array; // 声明一个数组 var arr = Array('blue','red','110','120'); // 字符串测试 var str = 'red'; var isInArray = str.in_array(arr); alert(isInArray); // true // 数字测试 var num = 119; var isInArray = num.in_array(arr); alert(isInArray); // false
If the input is not an array, an exception will be thrown
/** * JS判断一个值是否存在数组中 */ // 定义一个判断函数 var in_array = function(arr){ // 判断参数是不是数组 var isArr = arr && console.log( typeof arr==='object' ? arr.constructor===Array ? arr.length ? arr.length===1 ? arr[0]:arr.join(','):'an empty array': arr.constructor: typeof arr ); // 不是数组则抛出异常 if(!isArr){ throw "arguments is not Array"; } // 遍历是否在数组中 for(var i=0,k=arr.length;i<k;i++){ if(this==arr[i]){ return true; } } // 如果不在数组中就会返回false return false; } // 给字符串添加原型 String.prototype.in_array = in_array; // 给数字类型添加原型 Number.prototype.in_array = in_array; // 声明一个数组 var arr = null; // 字符串测试 var str = 'red'; var isInArray = str.in_array(arr); alert(isInArray); // uncaught exception: arguments is not Array
Report an error directly:

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