how to find index of an array element

Question

var styles = ['btx btx1', 'btx btx2', 'btx btx3', 'btx btx4'];

$('#mst').on('click', function(){
    let a = $('#btx').attr('class');
    console.log(a);  // `btx btx2`
    let x = styles.findIndex(a);
    console.log(x);  // error
});

error - Uncaught TypeError: btx btx2 is not a function

I'm expecting 1 as the result

I think you meant indexOf rather than findIndex, which expects a function parameter, as the error tells you. VTC as typo/resolved in a way unhelpful to future visitors. — ggorlen
– ggorlen, Commented Feb 22, 2020 at 19:52
@ggorlen - what about this - https://www.w3schools.com/jsref/jsref_findindex.asp — qadenza
– qadenza, Commented Feb 22, 2020 at 19:55
What about it? It says the same thing as above which is that you need to pass a function to findIndex. You could do this with styles.findIndex(e => e === a); but this is a more verbose and less efficient way to write styles.indexOf(a). — ggorlen
– ggorlen, Commented Feb 22, 2020 at 19:59

harsh_apache · Accepted Answer · 2020-02-22 19:52:32Z

3

Use indexOf:

$('#mst').on('click', function(){
   let a = $('#btx').attr('class');
   console.log(a);  // `btx btx2`
   let x = styles.indexOf(a);
   console.log(x);  // error
});

answered Feb 22, 2020 at 19:52

harsh_apache

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2 Comments

qadenza Over a year ago

what about this - https://www.w3schools.com/jsref/jsref_findindex.asp

harsh_apache Over a year ago

see this link, explained very well: stackoverflow.com/questions/41443029/…

Nguyễn Văn Phong · Accepted Answer · 2020-02-23 00:39:56Z

1

If you want to use findIndex(), the params must be function instead of a specific item.

Syntax

array.findIndex(function(currentValue, index, arr), thisValue)

var styles = ['btx btx1', 'btx btx2', 'btx btx3', 'btx btx4'];

let a = 'btx btx2';
let x = styles.findIndex(function(currentValue, index, arr){
  return currentValue === a;
});

console.log(x);

Or use indexOf()

The indexOf() method searches the array for the specified item, and returns its position.

var styles = ['btx btx1', 'btx btx2', 'btx btx3', 'btx btx4'];

let a = 'btx btx2';
let x = styles.indexOf(a);

console.log(x);

answered Feb 23, 2020 at 0:39

Nguyễn Văn Phong

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1 Comment

Nguyễn Văn Phong Over a year ago

@qadenza Does this answer your question? Let me know if you need any help

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