How to implement in_array using js_basic knowledge-JS Tutorial-php.cn

How to implement in_array using js_basic knowledge

WBOY

Release： 2016-05-16 17:17:30

Original

1540 people have browsed it

In js, we cannot directly judge a value or string by using in_array in an array like in php, because js does not have an in_array function, but we can customize an in_array function for js. I have collected a few below .
Example 1

Copy code The code is as follows:

function in_array(stringToSearch, arrayToSearch) {
 for (s = 0; s < arrayToSearch.length; s ) {
 thisEntry = arrayToSearch[s].toString();
 if (thisEntry == stringToSearch) {
 return true ;
 }
 }
 return false;
}

Example 2

Copy code The code is as follows:

var a = Array(1,2,3,4,5);
function in_array(search,array){
 for( var i in array){
                                                                                                                                                                                                                                                                         (11,a));
 

Example 3

Copy code

The code is as follows: /*** JS determines whether a value exists in an array * Qiongtai Blog */

// Define a judgment function

var in_array = function(arr){ 
// Judge whether the parameter is an array 
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 
);
// If it is not an array, an exception is thrown 
if(!isArr){ 
throw "arguments is not Array"; 
}
// Traverse whether it is in the array 
for(var i=0,k=arr.length;iif(this==arr[i]) { 
return true; 
} 
}
// If it is not in the array, it will return false 
return false; 
}
// Add a prototype to the string 
String.prototype.in_array = in_array; 
//Add a prototype to the number type
Number.prototype.in_array = in_array;
//Declare an array
var arr = Array('blue', 'red','110','120');
// String test
var str = 'red'; 
var isInArray = str.in_array(arr); 
alert(isInArray ); // true
//Number test
var num = 119; 
var isInArray = num.in_array(arr); 
alert(isInArray); // false 
if passed in If it is not an array, an exception will be thrown 
/**
* JS determines whether a value exists in an array 
* Qiongtai Blog 
*/
// Define a judgment function 
var in_array = function(arr){ 
// Judge whether the parameter is an array
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 
);
// If it is not an array, an exception will be thrown 
if(!isArr){ 
throw "arguments is not Array"; 
}
// Traverse whether it is in the array 
for(var i=0,k=arr.length;iif(this== arr[i]){ 
return true; 
} 
}
// If it is not in the array, it will return false 
return false; 
}
// Give the character Add prototype to string
String.prototype.in_array = in_array; 
// Add prototype to number type
Number.prototype.in_array = in_array;
// Declare an array
var arr = null ;
//String test
var str = 'red'; 
var isInArray = str.in_array(arr); 
alert(isInArray); // uncaught exception: arguments is not Array 
JS determines whether there are duplicate values ​​in an array
var ary = new Array("111","22","33","111"); 
var s = ary.join(", ") ","; 
for(var i=0;iif(s.replace(ary[i] ",","").indexOf(ary[ i] ",")>-1) { 
alert("There are duplicate elements in the array: " ary[i]); 
break; 
} 
}
 
 
Summary
The three examples all implement the function of in_array function, and they can all determine whether a given element is in the array. My personal favorite is the last method, which is more comprehensive.