Question

If I have a JavaScript object such as:

var x = {foo: 42, bar: {fubar: true}}

then I can get the value true with var flag = x.bar.fubar. I’d like to be able to separate out and store the path "bar.fubar", then evaluate it dynamically. Something like:

var paths = ["bar.fubar", ...];
...
var flag = evalPath( x, paths[0] );

Obviously I could write a simple parser and evaluator for a basic path expression grammar. But under DRY principles I wonder if there’s already an existing way to do something like evalPath built-in to JavaScript, or a small library that would do the job? I also anticipate needing array indexes in the path expression in future.

Update Just to be clear, I’m not asking for code samples – my question is whether there’s existing code (built-in or library) I can re-use. Thanks to the contributors below for suggestions of code samples anyway! Note that none of them handle the array index requirement.

Answer 1

Doing a quick search, I came across JSONPath. Haven’t used it at all, but it looks like it might do what you want it to.

Example usage:

var x = {foo: 42, bar: {fubar: true}}
var res1 = jsonPath(x, "$.bar.fubar"); // Array containing fubar's value