How to make indexof() differentiate between two like numbers in an array

Question

I have an array say

x = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]

I am using javascript indexof() to check if an element exist or not in the array and if it doesn't exits to do something....

my problem is that when an element like, 1,2,3,4,5,6 doesn't exist in the array, it still judge elements like 10 for 1, 12 for 2, 13 for 3, 14 for 4, 15 for 5, 16 for 6. and so it will still return that the element exists eventhough it is not there

eg:

if x = [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]

this will still not work as it will see 10 as 1

if(data1.indexOf(1)===-1){											document.getElementById("s1").style.backgroundColor= "red";
    $("input[name='seat1']").attr("disabled", "disabled");
}

then your question makes no sense, because 1 does not match 10. please add the content of data1 and/or x. — Nina Scholz
– Nina Scholz, Commented Oct 17, 2016 at 11:29

Nina Scholz · Accepted Answer · 2016-10-17 11:25:35Z

1

You could parse the string and use indexOf as array method.

JSON.parse(data1).indexOf(1) ...

edited Oct 17, 2016 at 11:25

answered Oct 17, 2016 at 11:20

Nina Scholz

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4 Comments

Jonas Chinagorom Over a year ago

Scholz, I Just did this

Jonas Chinagorom Over a year ago

var Vals = JSON.parse(data1); if(Vals.indexOf(1)===-1){ document.getElementById("s1").style.backgroundColor= "red"; $("input[name='seat1']").attr("disabled", "disabled"); }

Nina Scholz Over a year ago

please perform console.log(typeof data1); in the code. what do you read at the console?

Prathik Rajendran M Over a year ago

Are you sure it is an array? For x = [10], x.indexOf(1) is not returning 0 for me, however if x = "10" then x.indexOf(1) is returning 0.

Emil S. Jørgensen · Accepted Answer · 2016-10-17 11:27:49Z

Array.indexOf works in any browser > IE8: MDN Browser compatibility

Polyfill It if you need to support anything.

// POLYFILL TO SUPPORT ANY BROWSER
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/indexOf#Polyfill
// Production steps of ECMA-262, Edition 5, 15.4.4.14
// Reference: http://es5.github.io/#x15.4.4.14
if (!Array.prototype.indexOf) {
  Array.prototype.indexOf = function(searchElement, fromIndex) {

    var k;

    // 1. Let o be the result of calling ToObject passing
    //    the this value as the argument.
    if (this == null) {
      throw new TypeError('"this" is null or not defined');
    }

    var o = Object(this);

    // 2. Let lenValue be the result of calling the Get
    //    internal method of o with the argument "length".
    // 3. Let len be ToUint32(lenValue).
    var len = o.length >>> 0;

    // 4. If len is 0, return -1.
    if (len === 0) {
      return -1;
    }

    // 5. If argument fromIndex was passed let n be
    //    ToInteger(fromIndex); else let n be 0.
    var n = +fromIndex || 0;

    if (Math.abs(n) === Infinity) {
      n = 0;
    }

    // 6. If n >= len, return -1.
    if (n >= len) {
      return -1;
    }

    // 7. If n >= 0, then Let k be n.
    // 8. Else, n<0, Let k be len - abs(n).
    //    If k is less than 0, then let k be 0.
    k = Math.max(n >= 0 ? n : len - Math.abs(n), 0);

    // 9. Repeat, while k < len
    while (k < len) {
      // a. Let Pk be ToString(k).
      //   This is implicit for LHS operands of the in operator
      // b. Let kPresent be the result of calling the
      //    HasProperty internal method of o with argument Pk.
      //   This step can be combined with c
      // c. If kPresent is true, then
      //    i.  Let elementK be the result of calling the Get
      //        internal method of o with the argument ToString(k).
      //   ii.  Let same be the result of applying the
      //        Strict Equality Comparison Algorithm to
      //        searchElement and elementK.
      //  iii.  If same is true, return k.
      if (k in o && o[k] === searchElement) {
        return k;
      }
      k++;
    }
    return -1;
  };
}

// TEST ARRAY
var arr = [0,1,2,3,4,6,7,8,9,10,12,13,14,16,17,18,20]
// TESTS
var offset = 0;
for(var i = 0; i <= 20; i++) {
  if(arr.indexOf(i) === -1) {
    console.log(i, "not found");
  } else  {
    console.log(i, "found")
  }
}

mvw · Accepted Answer · 2016-10-17 11:44:06Z

0

Your example snippet is not helpful, as it does not show the data ("data1") you are working on.

The behaviour you describe is not the one which one gets with your example array:

x = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16];

alert("indexOf(1):" + x.indexOf(1));
alert("indexOf(10):" + x.indexOf(10));
alert("indexOf(0):" + x.indexOf(0));

It works as intended.

Your real data proably contains strings and not integers.

answered Oct 17, 2016 at 11:44

mvw

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1 Comment

Jonas Chinagorom Over a year ago

ur solution works for ur case but i don't know why is not working for me, the elements of my array are integers not stings

shanks · Accepted Answer · 2016-10-17 11:45:41Z

0

I would convert them to strings like this.

function existsInArray(numberArrays, number){
       const numAsStrings = numberArrays.join(',').split(',')
       return numAsStrings.indexOf(String(number)) > -1
    }
    
    console.log(existsInArray([1,2,3,4,5,6,33], 33))
    //true
    
    console.log(existsInArray([1,2,3,4,5,6,33], 34))
    //false

Hope this helps.

edited Oct 17, 2016 at 11:45

answered Oct 17, 2016 at 11:37

shanks

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2 Comments

Jonas Chinagorom Over a year ago

the data1 is a json return data

shanks Over a year ago

Shouldnt matter as long as you pass an array into the function (and ofcourse the items are just numbers like you showed in your example)

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