javascript assign a function to a variable without running it

Question

I have defined a global variable ff and then call f1 to assign function f3 to it. When I call f2, f3 will running.

var ff;
function f1() { ff=f3; }
function f2() { ff(); }
function f3() { alert("hello"); }

but if f3 take a parameter as following

function f3(txt) { alert(txt); }

and I call f1 to assign ff as following

function f1() { ff=f3("hello"); }

f3 will run at the same time.

I don't want f3 running when I assign it to ff and I need pass a argument. How can I achieve this? A variable with () after it as if will make it a function and make it run.

CD.. · Accepted Answer · 2016-03-15 13:34:19Z

13

Try using bind:

ff = f3.bind(null, "hello")

The bind() method creates a new function that, when called, has its this keyword set to the provided value, with a given sequence of arguments preceding any provided when the new function is called.

answered Mar 15, 2016 at 13:34

CD..

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Comments

Andreas · Accepted Answer · 2016-03-15 13:36:33Z

1

You are assigning ff the value of the f3 call, in your second example, which is why it calls your function. You should make the assignment ff=f3, as you did initially. Then you can call ff with a parameter: ff("hello")

edited Mar 15, 2016 at 13:36

answered Mar 15, 2016 at 13:34

Andreas

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1 Comment

LING Over a year ago

I may assign f4 which takes different numbers of parameters to ff in f1 according to different condition. So I can not call ff with a parameter in f2.

Arsylum · Accepted Answer · 2016-03-15 13:44:59Z

0

What about this?

var ff;
function f1() { ff=f3; }
function f2() { ff('hello'); }
function f3(text) { alert(text); }

answered Mar 15, 2016 at 13:44

Arsylum

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1 Comment

Bhavesh Odedra Over a year ago

Please add some comments about your solution on why and how it solves the problem

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