Question

I have a JavaScript object that I’d like to add some properties to, but I don’t know what the names of the properties are until runtime.

Can I do this without using eval? If so, how?

var get_params = new Object();
var params = {'name':'john', 'age':'23'}; //actually not known until runtime
for (var i=0, len=params.length; i<len; ++i ){                                                  
        get_params.p[0] = p[1]; //How can I set p[0] as the object property?
    }
}

Answer 1

Since your code example has a malformed array, I will include 2 variations.

Variation 1 (params is an actual object and not an array):

var get_params = {}; // prefer literal over Object constructors.

var params = {'name':'john', 'age':'23'}; // @runtime (as object literal)

for (var key in params){
    if(params.hasOwnProperty(key)) { // so we dont copy native props
        get_params[key] = params[key];
    }
}

Variation 2 (param is an array containing objects):

var get_params = {}; // prefer literal over Object constructors.

var params = [{'name':'john'},{'age':'23'}]; // @runtime (as array literal)

for(var i=0,param;param=params[i];i++) {
    for (var key in param){
        if(param.hasOwnProperty(key)) {
            get_params[key] = param[key];
        }
    }
}

Enjoy.