I want to use the value of a variable to access an object.
Let's say I have an object named myobject.
I want to fill a variable with this name and use the variable to access the object.
Example:
var objname = 'myobject';
{objname}.value = 'value';
This question is related to
javascript
Use square bracket around variable name.
var objname = 'myobject';
{[objname]}.value = 'value';
If you already know the list of the possible varible names then try creating a new Object(iconObj) whose properties name are same as object names, Here in below example, iconLib variable will hold two string values , either 'ZondIcons' or 'MaterialIcons'. propertyName is the property of ZondIcons or MaterialsIcon object.
const iconObj = {
ZondIcons,
MaterialIcons,
}
const objValue = iconObj[iconLib][propertyName]
The object exists in some scope, so you can almost always access the variable via this syntax:
var objname = "myobject";
containing_scope_reference[objname].some_property = 'some value';
The only place where this gets tricky is when you are in a closed scope and you want access to a top-level local variable. When you have something like this:
(function(){
var some_variable = {value: 25};
var x = "some_variable";
console.log(this[x], window[x]); // Doesn't work
})();
You can get around that by using eval
instead to access the current scope chain ... but I don't recommend it unless you've done a lot of testing and you know that that's the best way to go about things.
(function(){
var some_variable = {value: 25};
var x = "some_variable";
eval(x).value = 42;
console.log(some_variable); // Works
})();
Your best bet is to have a reference to a name in an always-going-to-be-there object (like this
in the global scope or a private top-level variable in a local scope) and put everything else in there.
Thus:
var my_outer_variable = {};
var outer_pointer = 'my_outer_variable';
// Reach my_outer_variable with this[outer_pointer]
// or window[outer_pointer]
(function(){
var my_inner_scope = {'my_inner_variable': {} };
var inner_pointer = 'my_inner_variable';
// Reach my_inner_variable by using
// my_inner_scope[inner_pointer]
})();
I think Shaz's answer for local variables is hard to understand, though it works for non-recursive functions. Here's another way that I think it's clearer (but it's still his idea, exact same behavior). It's also not accessing the local variables dynamically, just the property of the local variable.
Essentially, it's using a global variable (attached to the function object)
// Here's a version of it that is more straight forward.
function doIt() {
doIt.objname = {};
var someObject = "objname";
doIt[someObject].value = "value";
console.log(doIt.objname);
})();
Which is essentially the same thing as creating a global to store the variable, so you can access it as a property. Creating a global to do this is such a hack.
Here's a cleaner hack that doesn't create global variables, it uses a local variable instead.
function doIt() {
var scope = {
MyProp: "Hello"
};
var name = "MyProp";
console.log(scope[name]);
}
You can set an objects property this way:
var obj = {};_x000D_
obj.whateverVarName = 'yourVal';_x000D_
console.log(obj);
_x000D_
One of the challenges I had with the answers is that it assumed that the object was a single level. For example,
const testObj = { testKey: 'testValue' }
const refString = 'testKey';
const refObj = testObj[refString];
works fine, but
const testObj = { testKey:
{ level2Key: 'level2Value' }
}
const refString = 'testKey.level2Key';
const refObj = testObj[refString];
does not work.
What I ended up doing was building a function to access multi-level objects:
objVar(str) {
let obj = this;
const parts = str.split('.');
for (let p of parts) {
obj = obj[p];
}
return obj;
}
In the second scenario, then, I can pass the string to this function to get back the object I'm looking for:
const testObj = { testKey:
{ level2Key: 'level2Value' }
}
const refString = 'testObj.testKey.level2Key';
const refObj = objVar[refString];
If object is in some namespace ie. Company.Module.Components.Foo
you can use this function:
CoffeeScript:
objByName: (name, context = window) ->
ns = name.split "."
func = context
for n, i in ns
func = func[n]
return func
Resulted Js:
objByName: function(name, context) {
var func, i, n, ns, _i, _len;
if (context == null) {
context = window;
}
ns = name.split(".");
func = context;
for (i = _i = 0, _len = ns.length; _i < _len; i = ++_i) {
n = ns[i];
func = func[n];
}
return func;
}
Then you can create a new object or do whatever. Note the parenthises through.
var o = new (objByName('Company.Module.Components.Foo'))
objByName('some.deeply.nested.object').value
This idea is borrowed from similar question: How to execute a JavaScript function when I have its name as a string
You could use eval
:
eval(variablename + ".value = 'value'");
When using the window[objname], please make sure the objname is global variables. Otherwise, will work sometime, and fail sometimes. window[objname].value.
var micro=[{'test':'hello'}];
var device = 'test';
console.log(micro[device]);
You can't do this in general, except at the window scope, where you can write window[objname].value = 'value';
Is it a global variable? If so, these are actually part of the window
object, so you can do window[objname].value
.
If it's local to a function, I don't think there's a good way to do what you want.
let players = [];
players[something] = {};
players[something].somethingElse = 'test';
console.log(players);
-> [ something: { somethingElse: 'test' } ];
Source: Stackoverflow.com