Manipulating JSON data sets

Question

So I have an array myarr[] of JSON objects in the form: { "a":"", "b":"" }

Are there efficient methods for getting an array of b:

[ myarr[0].b, myarr[1].b, myarr[2].b, ... ]

Or do I have to manually iterate through the myarr to build the array of b?

You will have to iterate the array, yes, but there are helper functions that can simplify the usage. — Bergi
– Bergi, Commented May 13, 2013 at 18:54
@dlackey: pluck for example as suggested (and re-implemented) in the answers. — Bergi
– Bergi, Commented Feb 27, 2014 at 18:21
@Bergi - Ah, thanks. I hand't heard of "pluck" and thought it was the name of am abstract value like people use "foo" and "bar". — HPWD
– HPWD, Commented Feb 27, 2014 at 18:26

Nirvana Tikku · Accepted Answer · 2013-05-13 17:58:27Z

2

Check out the underscore.js library.

I'd suggest checking out the implementation for pluck.

What you'd want to do is effectively: _.pluck(myarr, 'b')

answered May 13, 2013 at 17:58

Nirvana Tikku

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sixFingers · Accepted Answer · 2013-05-13 17:58:16Z

1

Why not have fun with prototypes and extend Array to obtain a handy and reusable function:

Array.prototype.pluck = function(key) {
    var i = this.length, 
        plucked = [];
    while(i --) {
        plucked[i] = this[i][key] || ""
    }

    return plucked;
}

With this one, you can do:

collection.pluck(keyName)

To get back your desired result. Check here for a working demo: http://jsfiddle.net/jYrNN/1/

answered May 13, 2013 at 17:58

sixFingers

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Bergi Over a year ago

Why the || ""? Just let the result be undefined.

adeneo · Accepted Answer · 2013-05-13 23:00:29Z

1

var b_arr = $.map(myarr, function(val, i) { return val.b; });

FIDDLE

or wihtout jQuery

var b_arr = myarr.map(function(val) { return val.b })
                 .filter(function(n){return n || false});

edited May 13, 2013 at 23:00

answered May 13, 2013 at 18:03

adeneo

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Bergi Over a year ago

OP doesn't use jQuery, so the native method might be more appropriate

NullPointerException · Accepted Answer · 2013-05-13 17:58:49Z

-1

jQuery does provide api to parse json

$.each(myarr, function(key,value)
  {
    alert(key);
    alert(value);
  });

answered May 13, 2013 at 17:58

NullPointerException

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1 Comment

Bergi Over a year ago

Neither does he need to parse JSON, nor do you use that method.

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