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

Roll your own toFixed function: for positive values Math.floor works fine.

function toFixed(num, fixed) {
    fixed = fixed || 0;
    fixed = Math.pow(10, fixed);
    return Math.floor(num * fixed) / fixed;
}

For negative values Math.floor is round of the values. So you can use Math.ceil instead.

Example,

Math.ceil(-15.778665 * 10000) / 10000 = -15.7786
Math.floor(-15.778665 * 10000) / 10000 = -15.7787 // wrong.