I have so far:
function func(f,x) {
alert(f(x));
}
func(function(x) {return x*x;},2);
This works, but i am thinking that passing function(x) {return x*x;}, is excessive and I could just pass x*x, as the idea is that I can supply (pretty much) any function.
I have tried:
function func(f,y) {
g=function() {return f;};
alert(g(y));
}
func(x*x,2);
amongst others, but I can't get it to work. Perhaps if I passed 'x*x' as a string..?
You're correct that the syntax is excessive, but for ES5 and before, that's just how it is.
However, in ES6 you can use the new "arrow function" lambda syntax:
func(x => x * x, 2);
See http://www.es6fiddle.net/i4o5uj2l/
FWIW, the above func isn't great since it only supports unary functions, i.e. those taking a single parameter. You could expand func to use ES6 "spread arguments":
function func(f, ...args) {
console.log(f.apply(this, args));
}
func((x, y) => x * y, 3, 7);
> 21
Well I have a way to do that using eval here http://jsfiddle.net/q5ayoszy/
function func(f,y) {
g=function()
{ x=y;
return eval(f);
};
alert(g(y));
}
func('x*x',2);
Note : I pass the expression as a string and then use it inside the function.
You just need to assign the value of y to the variable x inside the function so the eval evaluates correctly
The only way to do that with a string is by using the infamous eval: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/eval
var x = 2;
var y = eval("x * x"); //y = 4
But using eval is almost always a very bad idea.
You could use currying to break down the process into smaller functions:
function multiply(x) {
return function() {
return x*x;
}
}
var bytwo = multiply(2);
bytwo(); // 4
