CODEWITHSUNDEEP
javascriptjavascript-objects
Momen Zalabany
Momen Zalabany

Reputation: 9007

Get object property using array of object name and proerty name

I want to find object property dynamically from array that map to property location.

Example 

 Var objectA = { a:{b:1} };
 Var Names = ['objectA','a','b'];

Howa can i get value of b by looping over array Names ?

Upvotes: 0

Views: 50

Answers (3)

mdziekon
mdziekon

Reputation: 3627

Assuming objectA is available in the global scope (window.objectA), you could do something like this:

names.reduce(function (memo, value) {
    return memo[value]; 
}, window)

For any other "non-global" variable, you can create a getter function that takes the variable and the path (an array just like your names, but without the first value) as a parameter:

function nestedValue(obj, path) {
    return path.reduce(function (memo, value) {
         return memo[value];
    }, obj);
}

BTW, please note that Array.prototype.reduce() is a ES2015 feature, so if you need to be compatible with older browsers, you would have to use some variation of for loop for this task.

You could also check out lodash.get for more sophisticated solution (if you're willing to include it in your project).

Upvotes: 2

nitishagar
nitishagar

Reputation: 9413

You can use eval: eval(Names.join('.'))

Can use this with nodejs inside a sandbox:

const util = require('util');
const vm = require('vm');

const objectA = { a: { b: 1 }};
const Names = ['objectA', 'a', 'b'];

const sandbox = { objectA: objectA, Names: Names };
vm.createContext(sandbox);

for (var i = 0; i < 10; ++i) {
    vm.runInContext("var result = eval(Names.join('.'))", sandbox);
}
console.log(util.inspect(sandbox));

/* { 
     objectA: { a: { b: 1 } },
     Names: [ 'objectA', 'a', 'b' ],
     result: 1 
   }
*/

Upvotes: 1

Rob M.
Rob M.

Reputation: 36521

To do this without eval would require you store ObjectA as a property of another object that you could iterate over using the array keys. eval will work in this case though:

objectA = { a: { b: 1 }}
names = ['objectA', 'a', 'b']
alert(eval(names.join('.')))

Upvotes: 0

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