JSON find in JavaScript -


is there better way other looping find data in json? it's edit , delete.

for(var k in objjsonresp) {   if (objjsonresp[k].txtid == id) {     if (action == 'delete') {       objjsonresp.splice(k,1);     } else {       objjsonresp[k] = newval;     }     break;   } }

the data arranged list of maps. like:

[   {id:value, pid:value, cid:value,...},   {id:value, pid:value, cid:value,...},   ... ]

(you're not searching through "json", you're searching through array -- json string has been deserialized object graph, in case array.)

some options:

use object instead of array

if you're in control of generation of thing, have array? because if not, there's simpler way.

say original data:

[     {"id": "one",   "pid": "foo1", "cid": "bar1"},     {"id": "two",   "pid": "foo2", "cid": "bar2"},     {"id": "three", "pid": "foo3", "cid": "bar3"} ]

could following instead?

{     "one":   {"pid": "foo1", "cid": "bar1"},     "two":   {"pid": "foo2", "cid": "bar2"},     "three": {"pid": "foo3", "cid": "bar3"} }

then finding relevant entry id trivial:

id = "one"; // or whatever var entry = objjsonresp[id];

...as updating it:

objjsonresp[id] = /* new value */;

...and removing it:

delete objjsonresp[id];

this takes advantage of fact in javascript, can index object using property name string -- , string can literal, or can come variable id above.

putting in id-to-index map

(dumb idea, predates above. kept historical reasons.)

it looks need array, in case there isn't better way searching through array unless want put map on it, if have control of generation of object. e.g., have originally:

[     {"id": "one",   "pid": "foo1", "cid": "bar1"},     {"id": "two",   "pid": "foo2", "cid": "bar2"},     {"id": "three", "pid": "foo3", "cid": "bar3"} ]

the generating code provide id-to-index map:

{     "index": {         "one": 0, "two": 1, "three": 2     },     "data": [         {"id": "one",   "pid": "foo1", "cid": "bar1"},         {"id": "two",   "pid": "foo2", "cid": "bar2"},         {"id": "three", "pid": "foo3", "cid": "bar3"}     ] }

then getting entry id in variable id trivial:

var index = objjsonresp.index[id]; var obj = objjsonresp.data[index];

this takes advantage of fact can index objects using property names.

of course, if that, have update map when modify array, become maintenance problem.

but if you're not in control of generation of object, or updating map of ids-to-indexes code and/ora maintenance issue, you'll have brute force search.

brute force search (corrected)

somewhat ot (although did ask if there better way :-) ), code looping through array incorrect. details here, can't use for..in loop through array indexes (or rather, if do, have take special pains so); for..in loops through properties of object, not indexes of array. best bet non-sparse array (and yours non-sparse) standard old-fashioned loop:

var k; (k = 0; k < somearray.length; ++k) { /* ... */ }

or

var k; (k = somearray.length - 1; k >= 0; --k) { /* ... */ }

whichever prefer (the latter not faster in implementations, counter-intuitive me, there are). (with sparse array, might use for..in again taking special pains avoid pitfalls; more in article linked above.)

using for..in on array seems work in simple cases because arrays have properties each of indexes, , other default properties (length , methods) marked non-enumerable. breaks set (or framework sets) other properties on array object (which valid; arrays objects bit of special handling around length property).


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