How do I call a JavaScript method based on a variable value?

Question

I have method a(), method b(), and method c(). I will get a response message from server, which contains a or b or c and so on. If the response message is a, then I need to call method a(). If the response message is b, then I need to call method b() And so on...

I don't want to write any if else conditions or switch case to identify the method.

I don't want to do this:

if(res == 'a')
   a();
else if(res == 'b')
   b();

Instead of that I need something like reflections in Java.

Satpal · Accepted Answer · 2017-01-24 09:13:17Z

8

If you have defined the function in Global/window Scope then you can directly use res variable

window[res]();

Otherwise define the function in object and then use it

var obj = {
    a : function(){},
    b : function(){}
}   
obj[res]();

edited Jan 24, 2017 at 9:13

answered Jan 24, 2017 at 9:11

Satpal

134k13 gold badges168 silver badges171 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Prasath Over a year ago

Thank you so much. Working fine.

Nina Scholz · Accepted Answer · 2017-01-24 09:12:34Z

6

You could use an object and store the function inside, like

var functions = {
    a: function () {},
    b: function () {},
    c: function () {}
    default: function () {} // fall back
}

Usage:

functions[res]();

Or with default

(functions[res] || functions.default)();

answered Jan 24, 2017 at 9:12

Nina Scholz

388k26 gold badges367 silver badges417 bronze badges

Comments

ollazarev · Accepted Answer · 2017-01-24 10:15:55Z

For this purpose you can define a class that allows you to define and call methods, and determine the calling context:

var MethodsWorker = function () {
    this._context = window;
    this._methods = {};
}

MethodsWorker.prototype.setContext = function (context) {
    this._context = context;
}

MethodsWorker.prototype.defineMethod = function (name, method) {
    this._methods[name] = method;
};

MethodsWorker.prototype.invoke = function (methodName, args) {
    var method = this._methods[methodName];
    if (!method) { throw {}; }
    return method.apply(this._context, args);
};

Usage:

var methodsWorker = new MethodsWorker ();
methodsWorker.setContext(Math);
methodsWorker.defineMethod('sqrtOfSum', function() {
    var sum = 0;
    for (var i = 0, n = arguments.length; i < n; i++) {
        sum += arguments[i];
    }
    return this.sqrt(sum);
});
var result = methodsWorker.invoke('sqrtOfSum', [1, 2, 3]);
alert (result);

Collectives™ on Stack Overflow

How do I call a JavaScript method based on a variable value?

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related