Say I have something that looks like this in javascripts:
var obj = {
subObj : {}
};
var type = 'subObj';
How can I get obj's subObj w/ type? For instance I would like to do something like:
obj.(type);
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5 Answers
obj[type]
You use subscript notation.
11.2.1 Property Accessors
Properties are accessed by name, using either the dot notation:
MemberExpression . IdentifierName
CallExpression . IdentifierName
or the bracket notation:
MemberExpression [ Expression ]
CallExpression [ Expression ]
1 Comment
sspboyd
Updated link to Property Accessors documentation: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…
You can treat objects like associative arrays in JavaScript, so you'll be able to access the inner object like:
var obj = {
subObj : {}
};
var type = "subObj";
var subObj = obj[type];
Comments
In case someone was wondering how to access sub properties (dynamically), I have found a way for that, if there's an easier way, please let me know:
function getPropertyByKeyPath(targetObj, keyPath) {
var keys = keyPath.split('.');
if(keys.length == 0) return undefined;
keys = keys.reverse();
var subObject = targetObj;
while(keys.length) {
var k = keys.pop();
if(!subObject.hasOwnProperty(k)) {
return undefined;
} else {
subObject = subObject[k];
}
}
return subObject;
}
For example this:
var o = {result : {info:{ version:1, comment: 'test'}}};
var subObject = getPropertyByKeyPath(o, 'result.info');
console.log(subObject);
would result in:
{version: 1, comment: "test"}
Comments
obj[type]
doesnt make any sense at all - you're not accessing TYPES, these are simple PROPERTIES - one could access them via obj[keyName] or something similar but using type is extremely confusing and a sure sign of lack of understanding
1 Comment
iuppiter
Well, properties are types. If you "console.log(typeof(obj.subObj));", it will return "object" to stdout. However properties can be accesses either by "obj.subObj" or "obj['subObj']" not "obj[subObj]". The latter will not work because the name of the object in brackets must be presented as a string.
var obj = {
subObj : {}
}
var type = 'subObj';
console.log(typeof obj.subObj); //will print "object"
console.log(obj.subObj); //will print "{}"
//You can add a new propery like this:
obj.subObj.newProperty = 'hello';
console.log(typeof obj.subObj.newProperty); //will print "string"
console.log(obj.subObj.newProperty); //will print "hello"
// you can also add new properties like this
obj.subObj['newProperty'] = 5; // this is very useful if you have to add properties with names that use reserved words or that contain illegal characters.
console.log(typeof obj.subObj.newProperty); //will print "number"
console.log(obj.subObj.newProperty); //will print "5"
//In the case where you're using reserved or illegal words you'l have to do this
obj.subObj['new/Property'] = 'cat'; // this is very useful if you have to add properties with names that use reserved words or that contain illegal characters.
console.log(typeof obj.subObj['new/Property']); //will print "number"
console.log(obj.subObj['new/Property]); //will print "5"
// and add another property in the chain:
obj.subObj['new/PropertyGroup']={
'illegal/name':'value',
acceptableName: 5,
andotherObject:{},
'illegally&Named(object)':{}
}
