How can I log an ArrayIndex out of bound in JavaScript?

Question

I have the array var john = ['asas','gggg','ggg'];

If I access john at index 3, ie. john[3], it fails.

How can I display a message or alert saying that there is no value at that index?

Michael Berkowski · Answer 1 · 2012-12-14T13:51:32.523

6

if (typeof yourArray[undefinedIndex] === "undefined") {
  // It's undefined
  console.log("Undefined index: " + undefinedIndex;
}

edited Dec 14 '12 at 13:51

answered Jun 29 '11 at 13:21

Michael Berkowski

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His question: **how can i display a message or alert saying that there is no value for the index passed.** – ssapkota Jun 29 '11 at 13:33
"Array index out of bounds" and "array has 'undefined' element" should be handled differently. See here: http://stackoverflow.com/questions/6728424/array-out-of-bounds-comparison-with-undefined-or-length-check – Vladislav Rastrusny Aug 22 '16 at 11:32

score 6 · Accepted Answer · answered Jun 29 '11 at 13:22

6

function checkIndex(arrayVal, index){
    if(arrayVal[index] == undefined){
        alert('index '+index+' is undefined!');
        return false;
    }
    return true;
}

//use it like so:
if(checkIndex(john, 3)) {/*index exists and do something with it*/}
else {/*index DOES NOT EXIST*/}

answered Jun 29 '11 at 13:22

Naftali

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dont try to cast the type! use === instead of == ! It'll be faster as well (by nanoseconds, but hey! :) – japrescott Oct 03 '12 at 15:12
"Array index out of bounds" and "array has 'undefined' element" should be handled differently. See here: http://stackoverflow.com/questions/6728424/array-out-of-bounds-comparison-with-undefined-or-length-check – Vladislav Rastrusny Aug 22 '16 at 11:31

score 2 · Answer 3 · answered Jun 29 '11 at 13:23

2

Javascript has try catch

try
  {
  //your code
  }
catch(err)
  {
  //handle the error - err i think also has an exact message in it.
alert("Error");
  }

answered Jun 29 '11 at 13:23

Yogurt The Wise

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Or check the length of the array. – Yogurt The Wise Jun 29 '11 at 13:24
if(somearray.length < 3 ) { then do something } – Yogurt The Wise Jun 29 '11 at 13:24
1

It is a crappy solution to catch index out of error and just swallow it. This kind of programming leads to bugs. It is better to just check the length of the array! – mortb Feb 09 '16 at 12:50
Javascript doesn't throw an exception when you access an out of bounds value. So, I'm not clear how this at all answers the question asked. – stuckj May 05 '22 at 19:41

score 1 · Answer 4 · answered Jun 29 '11 at 13:22

1

Javascript arrays start at 0. so your array contains contents 0 - 'asas', 1 - 'gggg', 2 - 'ggg'.

answered Jun 29 '11 at 13:22

CatchingMonkey

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score 1 · Answer 5 · answered Jun 29 '11 at 13:29

1

var john = ['asas','gggg','ggg'];
var index=3;
if (john[index] != undefined ){
 console.log(john[index]);
}

answered Jun 29 '11 at 13:29

ssapkota

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score 0 · Answer 6 · answered Jun 29 '11 at 13:21

0

Arrays are indexed starting with 0, not 1.

There are 3 elements in the array; they are:

john[0] // asas
john[1] // gggg
john[2] // ggg

answered Jun 29 '11 at 13:21

gen_Eric

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How can I log an ArrayIndex out of bound in JavaScript?

6 Answers6