Truncate number to two decimal places without rounding

Question

Suppose I have a value of 15.7784514, I want to display it 15.77 with no rounding.

var num = parseFloat(15.7784514);
document.write(num.toFixed(1)+\"


        

Answer 1

Convert the number into a string, match the number up to the second decimal place:

function calc(theform) {
    var num = theform.original.value, rounded = theform.rounded
    var with2Decimals = num.toString().match(/^-?\d+(?:\.\d{0,2})?/)[0]
    rounded.value = with2Decimals
}

Original number: 

"Rounded" number: 

The toFixed method fails in some cases unlike toString, so be very careful with it.