Deleting specific elements (objects) inside array

Question

I've tried to delete multiple entries in an array.

These entries are objects and I need to locate the object meeting specific criteria.

    var pending = [];
    a.forEach(function(entry, index) {
        if(entry.b == data) {
            pending.push(index);
        }
    });
    pending.forEach(function(entry) {
        a.splice(entry, 1);
    });

The problem is that it only deletes half of what I want (when b = data) and even deletes some random entries...

Thank you for your help.

What's in a, what is data? What are you trying to keep, show us some relevant (albeit simplified) code, with variables filled in? — David Thomas
– David Thomas, Commented Oct 11, 2014 at 21:22
Its possible that you're getting false positives from your non-strict equality comparison. Have you stepped through this in the debugger? — Jared Smith
– Jared Smith, Commented Oct 11, 2014 at 21:23
With each splice(), the indexes in a shift for everything > entry, so the next entry is off by 1, next by 2, etc. Look into .filter(). — Jonathan Lonowski
– Jonathan Lonowski, Commented Oct 11, 2014 at 21:23
AHH~! that's right @JonathanLonowski! I've overlooked that fact! So .filter()?? — cloud1250000
– cloud1250000, Commented Oct 11, 2014 at 21:26
@cloud1250000 Yeah. David already posted an example of .filter(). It isn't a mutator like .splice(), so it won't alter a. It instead creates a new Array without the filtered element that you can assign back into a as a = a.filter(...);. — Jonathan Lonowski
– Jonathan Lonowski, Commented Oct 11, 2014 at 21:40

David Thomas · Accepted Answer · 2014-10-11 21:24:55Z

2

I'm assuming that a is an array of objects, that you want to filter in order to keep only those whose b property is equal to the string 'data'. That being the case:

// this outputs to the console, you should probably press 'F12'
var a = [{
    'b': 'data'
  }, {
    'b': 'something else'
  }, {
    'b': 'data'
  }, {
    'b': 50
  }],
  pending = a.filter(function(elem) {
    return elem.b === 'data';
  });

console.log(pending);

References:

Array.prototype.filter().

answered Oct 11, 2014 at 21:24

David Thomas

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2 Comments

cloud1250000 Over a year ago

So basically, I should redo an array where I keep the message I want?

cloud1250000 Over a year ago

Perfect! it's working great! I did that pending = a.filter(function(elem) { return elem.b != data; }); a = pending;

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