Javescript basic question about function

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function formatAmount() {
	return "$" + amount.toFixed( 2 );
}

var amount = 99.99;
var kk = 11.11;

amount = formatAmount();
kk = formatAmount(); //TypeError: amount.toFixed is not a function (line 2 in function formatAmount)

console.log(amount); //"$99.99"

What I have tried:

I have two questions:

1.
Why it is OK to assign function formatAmount() to amount but not OK to do so to kk?

2.
If I assign function formatAmount() to amount, then the value of amount is no longer 99.99, right? Then why the output of amount.toFixed( 2 ) in console.log(amount) is still 99.99?

Posted 24-Nov-17 0:07am

Member 13539113

Updated 24-Nov-17 0:23am

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F-ES Sitecore · Accepted Answer · 2017-11-24T00:23:00

function formatAmount() {
	return "$" + amount.toFixed( 2 );
}
 
var amount = 99.99; // amount is 99.99 so is numeric
var kk = 11.11;
 
amount = formatAmount(); // after formatAmount amount is "$99.99" so is string
kk = formatAmount(); // you are now trying to use toFixed on a string which you can't do, it worked before because amount was numeric before

You should change your formatAmount function so that it takes the value to format as a param rather than acting on a global variable.

function formatAmount(a) {
    return "$" + a.toFixed(2);
}

var amount = 99.99;
var kk = 11.11;

var amountF = formatAmount(amount);
var kkF = formatAmount(kk);

console.log(amountF); 
console.log(kkF);