Determine whether an array contains a value [dupli

Question

This question already has an answer here:

• How do I check if an array includes an object in JavaScript? 44 answers

I need to determine if a value exists in an array.

I am using the following function:

Array.prototype.contains = function(obj) {
    var i = this.length;
    while (i--) {
        if (this[i] == obj) {
            return true;
        }
    }
    return false;
}

The above function always returns false.

The array values and the function call is as below:

arrValues = ["Sam","Great", "Sample", "High"]
alert(arrValues.contains("Sam"));

Answer 1

My little contribution:

function isInArray(array, search)
{
    return array.indexOf(search) >= 0;
}

//usage
if(isInArray(my_array, "my_value"))
{
    //...
}

Answer 2

I prefer simplicity:

var days = [1, 2, 3, 4, 5];
if ( 2 in days ) {console.log('weekday');}

Answer 3

function setFound(){   
 var l = arr.length, textBox1 = document.getElementById("text1");
    for(var i=0; i<l;i++)
    {
     if(arr[i]==searchele){
      textBox1 .value = "Found";
      return;
     }
    }
    textBox1 .value = "Not Found";
return;
}

This program checks whether the given element is found or not. Id text1 represents id of textbox and searchele represents element to be searched (got fron user); if you want index, use i value

Answer 4

Given the implementation of indexOf for IE (as described by eyelidlessness):

Array.prototype.contains = function(obj) {
    return this.indexOf(obj) > -1;
};

Answer 5

Array.prototype.includes()

In ES2016, there is Array.prototype.includes().

The includes() method determines whether an array includes a certain element, returning true or false as appropriate.

Example

["Sam", "Great", "Sample", "High"].includes("Sam"); // true

Support

According to kangax and MDN, the following platforms are supported:

• Chrome 47
• Edge 14
• Firefox 43
• Opera 34
• Safari 9
• Node 6

Support can be expanded using Babel (using babel-polyfill) or core-js. MDN also provides a polyfill:

if (![].includes) {
  Array.prototype.includes = function(searchElement /*, fromIndex*/ ) {
    'use strict';
    var O = Object(this);
    var len = parseInt(O.length) || 0;
    if (len === 0) {
      return false;
    }
    var n = parseInt(arguments[1]) || 0;
    var k;
    if (n >= 0) {
      k = n;
    } else {
      k = len + n;
      if (k < 0) {k = 0;}
    }
    var currentElement;
    while (k < len) {
      currentElement = O[k];
      if (searchElement === currentElement ||
         (searchElement !== searchElement && currentElement !== currentElement)) {
        return true;
      }
      k++;
    }
    return false;
  };
}

Answer 6

If you have access to ECMA 5 you can use the some method.

MDN SOME Method Link

arrValues = ["Sam","Great", "Sample", "High"];

function namePresent(name){
  return name === this.toString();
}
// Note:
// namePresent requires .toString() method to coerce primitive value
// i.e. String {0: "S", 1: "a", 2: "m", length: 3, [[PrimitiveValue]]: "Sam"}
// into
// "Sam"

arrValues.some(namePresent, 'Sam');
=> true;

If you have access to ECMA 6 you can use the includes method.

MDN INCLUDES Method Link

arrValues = ["Sam","Great", "Sample", "High"];

arrValues.includes('Sam');
=> true;