Call Javascript function from string - javascript

Is it possible to call a function in javascript from a string, where the function is in an object?
e.g: call "main.object.doSomething()" (notice it is a string) from the object below.
window.main = {
object: {
doSomething: function(){
alert('Called');
}
}
}
--- Update ---
...without using eval();

window.main = {
object: {
doSomething: function(){
alert('Called');
}
}
}
function callFromString(aString) {
var parts = aString.split(".");
var obj = window;
for (var i = 0; i < parts.length - 1; i++) {
obj = obj[parts[i]];
if (!obj)
return;
}
// strip () at the end of parts[parts.length - 1] if they are present
if (obj[parts[parts.length - 1]])
obj[parts[parts.length - 1]]();
}
callFromString("main.object.doSomething");
http://jsfiddle.net/79nWH/

You can use eval, so:
eval("main.object.doSomething()");
But eval is evil - try to avoid it.

Do not use eval! There are many good reasons not to use eval, and most of the time there's absolutely no reason to do so. Instead, you can use the string property lookup syntax to get the method you're looking for: main.object.doSomething() is equivalent to main.object['doSomething'](). So, for example, if you want to call a function based on a string, you could do:
var methodToCall = 'doSomething';
main.object[methodToCall]();
If putting the parentheses right after the property lookup looks weird to you, you could also do main.object[methodToCall].call(null).

use eval(expression or function)
read about that in http://www.w3schools.com/jsref/jsref_eval.asp
or http://viralpatel.net/blogs/calling-javascript-function-from-string/

Lets say you have your string like:
var funcString = "window.main = {
object: {
doSomething: function(){
alert('Called');
}
}
}";
eval(funcString);
and if you have already your function defined in the page, you can call it with 2 different ways, using eval (which no js expert would never offer using it, you should use it just when you don't have any other option):
eval("main.object.doSomething()");
and the other way is using anonymous function:
Function("main.object.doSomething();")();

Related

Function chaining with function names from list [duplicate]

What is the equivalent code of window["functionName"](arguments) in NodeJS server-side?
If you need such a capability within a module, one hack is to store such module functions in variables within the module and then call them by accessing them from the module object properties. Example:
var x = { }; // better would be to have module create an object
x.f1 = function()
{
console.log('Call me as a string!');
}
Now, within the module, you can call it using the value from a string:
var funcstr = "f1";
x[funcstr]();
I am learning the ropes with Node myself, the above is probably all sorts of wrong :-). Perhaps a marginally better way to write this example would be (for the module m.js):
module.exports =
{
f1: function() { console.log("Call me from a string!"); },
f2: function(str1) { this[str1](); }
}
Now you can:
var m = require('m.js');
m.f2('f1');
Or even just:
var m = require('m.js');
m['f1']();
FWIW!
you're looking for global
Note, however, that in modules nothing is ever exposed to this level
1) If methods are in same js file
define all methods as properties of Handler:
var Handler={};
Handler.application_run = function (name) {
console.log(name)
}
Now call it like this
var somefunc = "application_run";
Handler[somefunc]('jerry codes');
Output: jerry codes
2) If you want to keep methods in a different js file
// Handler.js
module.exports={
application_run: function (name) {
console.log(name)
}
}
Use method defined in Handler.js in different.js:
// different.js
var methods = require('./Handler.js') // path to Handler.js
methods['application_run']('jerry codes')
Output: jerry codes
If you want to call a class level function using this then following is the solution and it worked for me
class Hello {
sayHello(name) {
console.log("Hello " + name)
}
callVariableMethod() {
let method_name = 'sayHello'
this[`${method_name}`]("Zeal Nagar!")
}
}
If You need it in module scope, You can use something like this
var module = require('moduleName');
module['functionName'](arguments);
Honestly, looking at all these answers they seem a bit too much work. I was playing around to look for other ways around this. You can use the eval() command to print a variable as text then call it as a function
I.e
let commands = ['add', 'remove', 'test'];
for (i in commands) {
if (commands[i] == command) {
var c = "proxy_"+command;
eval(c)(proxy);
}
}
eval(string)(arg1, arg2);
This example script would execute the function proxy_test(proxy)
You know, the OP's code inspired me to try this:
global.test = function(inVal){
console.log(inVal);
}
global['test']('3 is the value')
But now that I think about it, it's no better than #Ravi' s answer.
I use this for node, see if this approach works for you
var _ = require('lodash');
var fnA1 = require('functions/fnA1');
var fnA2 = require('functions/fnA2');
module.exports = {
run: function(fnName, options, callback) {
'use strict';
var nameSpace = fnName.toString().split('.');
// if function name contains namespace, resolve that first before calling
if (nameSpace.length > 1) {
var resolvedFnName = this;
_.forEach(nameSpace, function(name){
resolvedFnName = resolvedFnName[name];
});
resolvedFnName(options, callback);
} else {
this[fnName](options, callback);
}
},
fnA1: fnA1,
fnA2: fnA2
};
call this like
importVariable.run('fnA1.subfunction', data, function(err, result){
if (err) {return callback(err);}
return callback(null, result);
});
That is not specific to the window object. In JavaScript any property of the object can be accessed this way. For example,
var test = {
prop1 : true
};
console.log(test.prop1); // true
console.log(test["prop1"]); // also true
Read more here : https://developer.mozilla.org/en/JavaScript/Guide/Working_with_Objects

dynamic call to a function jQuery

I am trying to build a lib and I need to call functions dynamically depending on the variables I have in parameter like this
strategies = min
function dispatchRuleToStrategy(strategies)
{
$.each(strategies, function(index, value) {
strategy = "strategy_" + value;
});
}
function strategy_min()
{
// do something
}
How can I call the function strategy_min() from dispatchRuleToStrategy()?
I've been trying a couple of things none of which are working.
Thanks for your help
Use an Object to create a dictionary of your functions e.g. lib
var lib = {
'strategy_min': strategy_min
};
then you can invoke via the key in this dictionary Object
lib['strategy_min']();
If you've named all your functions and you don't want to re-type the names over and over, you could
var lib = {};
function addToLib(fn) {
lib[fn.name] = fn;
}
// then
addToLib(strategy_min);
// or
[strategy_min].forEach(addToLib);
Put them in an object and use the property name:
var strategy_table = {
min: function() {
// do something
},
max: function() {
// do something else
},
...
};
Then you can access them as strategy_table[value]:
$.each(strategies, function(index, value) {
strategy_table[value]();
});
Others have already suggested to create a wrapper object for the functions, however, if your strategy_min() function is in the global scope, you can access it directly:
window['strategy_' + value]();
window in browsers refers to the global object. The bracket notation is used to access properties whose keys are dynamically generated. This way you are accessing the function, which is a property of the global object, i.e. window, and calling it using the parentheses.
Finally I found the real problem. I was in a jquery document ready which is a closure. I did not knew what closures were before today.
Thanks all for your help
You can use eval() function in the following manner
$.each(strategies, function(index, value) {
strategy = "strategy_" + value;
eval(strategy+"()");
});

Equivalent of "window["functionName"](arguments)" in server-side

What is the equivalent code of window["functionName"](arguments) in NodeJS server-side?
If you need such a capability within a module, one hack is to store such module functions in variables within the module and then call them by accessing them from the module object properties. Example:
var x = { }; // better would be to have module create an object
x.f1 = function()
{
console.log('Call me as a string!');
}
Now, within the module, you can call it using the value from a string:
var funcstr = "f1";
x[funcstr]();
I am learning the ropes with Node myself, the above is probably all sorts of wrong :-). Perhaps a marginally better way to write this example would be (for the module m.js):
module.exports =
{
f1: function() { console.log("Call me from a string!"); },
f2: function(str1) { this[str1](); }
}
Now you can:
var m = require('m.js');
m.f2('f1');
Or even just:
var m = require('m.js');
m['f1']();
FWIW!
you're looking for global
Note, however, that in modules nothing is ever exposed to this level
1) If methods are in same js file
define all methods as properties of Handler:
var Handler={};
Handler.application_run = function (name) {
console.log(name)
}
Now call it like this
var somefunc = "application_run";
Handler[somefunc]('jerry codes');
Output: jerry codes
2) If you want to keep methods in a different js file
// Handler.js
module.exports={
application_run: function (name) {
console.log(name)
}
}
Use method defined in Handler.js in different.js:
// different.js
var methods = require('./Handler.js') // path to Handler.js
methods['application_run']('jerry codes')
Output: jerry codes
If you want to call a class level function using this then following is the solution and it worked for me
class Hello {
sayHello(name) {
console.log("Hello " + name)
}
callVariableMethod() {
let method_name = 'sayHello'
this[`${method_name}`]("Zeal Nagar!")
}
}
If You need it in module scope, You can use something like this
var module = require('moduleName');
module['functionName'](arguments);
Honestly, looking at all these answers they seem a bit too much work. I was playing around to look for other ways around this. You can use the eval() command to print a variable as text then call it as a function
I.e
let commands = ['add', 'remove', 'test'];
for (i in commands) {
if (commands[i] == command) {
var c = "proxy_"+command;
eval(c)(proxy);
}
}
eval(string)(arg1, arg2);
This example script would execute the function proxy_test(proxy)
You know, the OP's code inspired me to try this:
global.test = function(inVal){
console.log(inVal);
}
global['test']('3 is the value')
But now that I think about it, it's no better than #Ravi' s answer.
I use this for node, see if this approach works for you
var _ = require('lodash');
var fnA1 = require('functions/fnA1');
var fnA2 = require('functions/fnA2');
module.exports = {
run: function(fnName, options, callback) {
'use strict';
var nameSpace = fnName.toString().split('.');
// if function name contains namespace, resolve that first before calling
if (nameSpace.length > 1) {
var resolvedFnName = this;
_.forEach(nameSpace, function(name){
resolvedFnName = resolvedFnName[name];
});
resolvedFnName(options, callback);
} else {
this[fnName](options, callback);
}
},
fnA1: fnA1,
fnA2: fnA2
};
call this like
importVariable.run('fnA1.subfunction', data, function(err, result){
if (err) {return callback(err);}
return callback(null, result);
});
That is not specific to the window object. In JavaScript any property of the object can be accessed this way. For example,
var test = {
prop1 : true
};
console.log(test.prop1); // true
console.log(test["prop1"]); // also true
Read more here : https://developer.mozilla.org/en/JavaScript/Guide/Working_with_Objects

How to create javascript function lookup object?

I'm attempting to create a function lookup in Javascript essentially mapping a data type to a function that does something for that data type. Right now I have something similar to:
var Namespace = Namespace || {};
Namespace.MyObj = function () {
var stringFunc = function(someData) {
//Do some string stuff with someData
};
var intFunc = function(someData) {
//Do some int stuff with someData
};
var myLookUp = {
'string': stringFunc,
'int' : intFunc
};
return {
PublicMethod: function (dataType, someData) {
myLookUp[dataType](someData);
}
};
} ();
When I invoke Namespace.MyObj.PublicMethod(dataType, someData) I get an error that myLookUp is not defined. I'm assuming I'm not going about setting up the function lookup object correctly, but not sure how to do so. Thanks for any help.
The problem might simply be incorrect case
myLookup[dataType](someData);
should be (notice the capital U)
myLookUp[dataType](someData);
Just looked at my post after I wrote it up, stupid oversight, I'm declaring the properties as strings, instead of just properties.
....
var myLookUp = {
string: stringFunc,
int: intFunc
};
....
Fixes the issue.
Some additional follow up, in my actual code dataType is the result of a jQuery select. Don't know why or if this would be browser dependant (I'm using FireFox), but using double quotes around the property definition works, single quotes does not, and no quotes works as well. :-\

Change var in object literal function

Hi guys I am writing some code using the object literal pattern, I have function that returns a value:
'currentLocation': function() {
var cL = 0;
return cL;
},
I then need to update the variable 'cL' from another function like this:
teamStatus.currentLocation() = teamStatus.currentLocation() + teamStatus.scrollDistance();
This part is part of another function - however I get an error back stating: invalid assignment left-hand side
I am guessing I can not update the variable in this way, could anyone suggest a better method or point me in the right direction.
Any help would be greatly appreciated.
Going to add more code to highlight what I am trying to do:
'currentLocation': function() {
var cL = 0;
return cL;
},
'increaseTable': function() {
if (teamStatus.currentLocation() <= teamStatus.teamStatusTableHeight() ) {
teamStatus.currentLocation = teamStatus.currentLocation() + teamStatus.scrollDistance();
$("#tableTrackActual").animate({scrollTop: (teamStatus.currentLocation)});
$("#tableMembers").animate({scrollTop: (teamStatus.currentLocation) });
//console.log(teamStatus.currentLocation());
teamStatus.buttonRevealer();
}
}
As you can see increaseTable should update the value of currentLocation - help this sheds more light on what I am trying to achieve.
You're writing teamStatus.currentLocation() =, which calls the function teamStatus.currentLocation and tries to assign to the return value. That isn't valid. You want just teamStatus.currentLocation = — no function call.
The variable inside your function is completely private to that function (and any functions defined within it). If you need to create a number of functions that share a set of private variables, you can do that with a closure. For instance:
var Thing = (function() {
var thingWideData;
function getData() {
return thingWideData;
}
function setData(newData) {
thingWideData = newData;
}
return {
getData: getData,
setData: setData
};
})();
What that does is create a Thing object which has getData and setData functions available for it, which get and set the completely private thingWideData variable contained by the anonymous closure. More about this pattern here and here, although the latter of those is more about private methods than private data.
What your code produces is:
0 = 0 + <some number>
Which variable do you want to update? cL? You are declaring it in the function, you cannot assign a value to it from outside. Depending on the rest of your code, you might be better off with getters and setters:
var object = {
_cL = 0,
get currentLocation() {
return this._cL;
},
set currentLocation(value) {
this._cL = value;
}
}
then you can do:
teamStatus.currentLocation = teamStatus.currentLocation + teamStatus.scrollDistance();
Update:
Regarding IE: If currentLocation should actually be just a number, it might be sufficient to just declare it as property:
var obj = {
currentLocation: 0
}

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