remove specific item from a json object

Question

i am trying to remove some items in an json object list, the ones that have a specific group. My JSON looks like this.

var events = [
        {"id":"19","name":"sports","group":"1"},
        {"id":"20","name":"school","group":"2"},
        {"id":"21","name":"fun","group":"1"}
    ]

I tried this

for(var i in events)
    if(events[i].group == deleted_group)
        events.splice(i, 1);

But the problem of this, is that if i have to remove more items, it bugs out. Is there another easy way to to this ? I am open for sugestion even using underscore.js .

Thank you in advance, Daniel!

tgpatel · Accepted Answer · 2014-01-15 22:45:59Z

1

Try this

var events = [
    {"id":"19","name":"sports","group":"1"},
    {"id":"20","name":"school","group":"2"},
    {"id":"21","name":"fun","group":"1"}
]

console.log(_.reject(events, function(event){ return event.group == '1'; }));

answered Jan 15, 2014 at 22:45

tgpatel

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2 Comments

Pacuraru Daniel Over a year ago

this works great, thank you very much and also to everyone on this topic

Karol Over a year ago

@PacuraruDaniel underscore solution is good indeed - I missed that you're using underscore in my answer. My answer is for people who don't want to use underscore and are interested in pure JS solution.

LJᛃ · Accepted Answer · 2014-01-15 22:46:15Z

0

When you're using the "splice" function to remove elements from the array inside a for loop, you need to shift your current index back when removing an item since the array is reindexed.

Also take a look at the array functions like "filter" for a more convenient way, read more on MDN.

answered Jan 15, 2014 at 22:46

LJᛃ

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1 Comment

Kyle Falconer Over a year ago

Filter seems to be the right answer to the question, however, IE<9 doesn't support Array.prototype.filter.

Karol · Accepted Answer · 2014-01-15 23:29:09Z

0

You can use delete operator to delete objects (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/delete):

delete events[0]

The problem with delete is, that in your array, as a value of events[0] it will leave undefined.

So another way (the way I would choose for your simple example) is to just rewrite the array:

var temp_events = [];
for(var i in events)
    if(events[i].group != deleted_group)
        temp_events[temp_events.length] = events[i];
events = temp_events;

Executing splice in a for loop has complexity n^2 (where n is number of elements). Rewriting has linear complexity.

answered Jan 15, 2014 at 23:29

Karol

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