javascript find object in array by value and append additional value

Question

I think the title explains it well enough. I've got an array that has two values per object and I need to look up the object by one of those values then assign a third to it.

Here are the guts:

$slides.push({
    img: el.attr('href'),
    desc: el.attr('title').split('Photo #')[1]
});

Which builds an array as such:

Object
    desc: 127
    img: img/aaron1.jpg
Object
    desc: 128
    img: img/aaron2.jpg

I'd like to look up the desc value, then assign a third value of in: yes

$slides.findInArray('desc', '127').addValueToObject('in','yes')

What is with the $ in the name? Basically you need to loop and compare. — epascarello, Oct 18 '12 at 02:53
it's a global variable; name doesn't much matter though. loop and compare? — technopeasant, Oct 18 '12 at 02:54
loop...aka for loop. look at each index of the array. Compare aka x==y, check each object's property for the value? Seems like a simple solution. The dollar sign makes no sense, sounds like you re trying to make JavaScript feel like another language with it there. — epascarello, Oct 18 '12 at 02:59
I usually add a dollar sign at the beginning of a variable if it's a jquery object, to remind myself that it's shorthand, for example `$this = $(this)`. Otherwise, yeah. Looks like you're trying to make it look like a different language. — Jan, Oct 18 '12 at 03:04

Matt Stone · Accepted Answer · 2012-10-18T04:04:20.037

http://jsfiddle.net/S3cpa/

var test = [
    {
        desc: 127,
        img: 'img/aaron1.jpg',
    },
    {
        desc: 128,
        img: 'img/aaron2.jpg',
    }
];

function getObjWhenPropertyEquals(prop, val)
{
    for (var i = 0, l = test.length; i < l; i++) {
        // check the obj has the property before comparing it
        if (typeof test[i][prop] === 'undefined') continue;

        // if the obj property equals our test value, return the obj
        if (test[i][prop] === val) return test[i];
    }

    // didn't find an object with the property
    return false;
}

// look up the obj and save it
var obj = getObjWhenPropertyEquals('desc', 127);

// set the new property if obj was found
obj.in = obj && 'yes';

Jan · Answer 2 · 2012-10-18T05:40:13.053

1

You need to run it through a for loop

// Loop through the array
for (var i = 0 ; i < $slides.length ; i++) 
{
    // Compare current item to the value you're looking for
    if ($slides[i]["desc"] == myValue)
    {
        //do what you gotta do
        $slides[i]["desc"] = newValue;
        break;
    }
}

edited Oct 18 '12 at 05:40

answered Oct 18 '12 at 02:57

Jan

5,688
3
27
44

continue will simply jump to the next loop iteration. You need to use the break; statement to exit the loop. – Matt Stone Oct 18 '12 at 04:05

Praveen Prasad · Answer 3 · 2012-10-18T04:00:46.057

1

easy way



 for (var i = 0; i < $slides.length; i++) 
    {
        if ($slides[i]["desc"] == "TEST_VALUE")
        {
            $slides[i]['in']='yes';
        }
    }

Another way

    Array.prototype.findInArray =function(propName,value)
    {
        var res={};
        if(propName && value)
        {
          for (var i=0; i<this.length; i++)
          {
            if(this[i][propName]==value)
            {
               res = this[i];
               break;
            }
          }
        }
        return res;
    }


    Object.prototype.addValueToObject =function(prop,value)
   {
        this[prop]=value;
   }

---Using It--

$slides.findInArray('desc', '127').addValueToObject('in','yes');

http://jsfiddle.net/s6ThK/

edited Oct 18 '12 at 04:00

answered Oct 18 '12 at 03:01

Praveen Prasad

31,561
18
73
106

2

When you find the correct object, you should break from the loop to avoid wasted loop cycles. – Matt Stone Oct 18 '12 at 03:13
User copied my code, including the error that was in it, then got correct answer? – Jan Oct 18 '12 at 03:30
@MattStone great point, i see why your answer is better. will adjust my acceptance. – technopeasant Oct 18 '12 at 03:33
@Jan didn't see or notice an error in either of yours. while you answered first, he answered more completely by including the 'in: yes' addition – technopeasant Oct 18 '12 at 03:34
Check the last closing bracket.. :) – Jan Oct 18 '12 at 03:35
@technopeasant: i have updated the answer, but for no check it once. – Praveen Prasad Oct 18 '12 at 04:02

score 1 · Answer 4 · answered May 28 '19 at 08:05

1

With modern JS it can be simply done:

var obj = $slides.find(e => e.desc === '127');
if (obj) {
    obj.in = 'yes';
}

answered May 28 '19 at 08:05

Alex Che

6,659
4
44
53

javascript find object in array by value and append additional value

4 Answers4