LinuxQuestions.org - Javascript, conditionals, higher-order functions

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Javascript, conditionals, higher-order functions

Hi. I'm playing around with Javascript until my book arrives. I was in the process of writing this small program as part of an on-line practice exercise:

Code:

function sum(a, b) { return a + b }



function difference(a, b) { return a - b }



function product(a, b) { return a * b }



function quotient(a, b) { return a / b }



function dispResult() {

  // put form values into variables

  a = window.document.calcform.a.value

  op = window.document.calcform.op.value

  b = window.document.calcform.b.value

  c = window.document.calcform.b.value



  // idea is to make opfunc a reference to a function

  // that I can pass on to some other function later on

  // (higher-order style)

  opfunc = if (op == "+") { sum }

            else if (op == "-") { difference }

              else if (op == "*") { product }

                else if (op == "/") { quotient }

                  else { null } 



  // other code will go here eventually

}

However, the compiler will not accept the first if statement. Question: do Javascript conditionals return values? If not, what would be the most similar working syntax to the above?

I dont see semi-colons...according to what I recall, statements should end with a semi-colon...

Quote:

function sum(a, b) { return a + b }

should probably be:

Quote:

function sum(a, b)
{
return a + b;
}

Or, the way I'd write it:

Quote:

function sum(a, b)
{
c = a + b;
return c;
}

...but, that's my style... :)

Luck

Thor

Javascript uses C-style syntax so statements cannot return values. You can use the ternary operator (which works the way you want if to work) though:

Code:

var opfunc =

    (op == "+")? sum :

    (op == "-")? difference :

    (op == "*")? product :

    (op == "/")? quotient :

    null

I think using an associative array/object would be a better idea:

Code:

var funcs = {"+": sum, "-": difference, "*": product, "/": quotient}

var opfunc = funcs[op]