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

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