where function of Linq.js on Json data not working

Question

How to correct following code for desired output,

var Data = [{ "A": -27, "B": -39 }, { "A": 28, "B": 0}]

var filter = "x[A]==28";

var findItem = Enumerable.From(Data)
 .Where(function (x) { return filter ; })
 .ToArray();

alert(findItem.length);

$.each(findItem, function (i, value) {
alert(value["A"]);
});

It should give me one value A:28 or complete one record { "A": 28, "B": 0}, why i am getting two values, How to get correct results ?

using "linq.js" from following path: [ https://raw.github.com/gist/1175460/fb7404d46cab20e31601740ab8b35d99a584f941/linq.js ]

code at JSfiddle: http://jsfiddle.net/Irfanmunir/gLXNw/2/

You're returning a string, which is "truthy" (evaluates to true). You probably want to actually evaluate your filter in the where callback: .Where(function (x) { return x['A'] == 28; }) — Shmiddty
– Shmiddty, Commented Jan 8, 2013 at 18:10
It will not work as i am passing a variable field for where clause. The solution mention below works — irfan Munir
– irfan Munir, Commented Jan 9, 2013 at 12:03
Can you update the linq.js path. The path you have given is broken, So all the jsfiddle are not working. — Rajon Tanducar
– Rajon Tanducar, Commented Jan 25, 2022 at 11:59

hereandnow78 · Accepted Answer · 2013-01-08 18:13:31Z

3

your filter is a string which always evaluates to true. put your filter inside a function:

var filter = function(x) { return x['A'] === 28 };

and use this:

.Where(filter)

see updated fiddle: http://jsfiddle.net/gLXNw/4/

answered Jan 8, 2013 at 18:13

hereandnow78

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2 Comments

irfan Munir Over a year ago

i need x['A'] === 28 in a variable, so I can create and pass filter at runtime to where clause.

hereandnow78 Over a year ago

then it should be fine to use @pimvdb's solution

pimvdb · Accepted Answer · 2013-01-08 18:27:08Z

2

You either have to pass a predicate function, or a string that represents such a function. You're passing a function, so linq.js doesn't expect another function/string.

For Linq.js, you have to use this syntax for a string:

var filter = "x => x['A']==28";  // also note the quotes surrounding A

You then pass this function string to .Where:

.Where(filter)

You can of course also inline this:

.Where("x => x['A']==28")

http://jsfiddle.net/gLXNw/3/

edited Jan 8, 2013 at 18:27

answered Jan 8, 2013 at 18:12

pimvdb

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3 Comments

hereandnow78 Over a year ago

i like your answer more ;-)

Shmiddty Over a year ago

@hereandnow78 The syntax mirrors Linq syntax, but I wouldn't be surprised if there's a significant performance hit for doing this.

pimvdb Over a year ago

@Shmiddty: I don't know how it's implemented, but such a string only has to be parsed once, and the real generated function can be reused thereafter.

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