Javascript中的乘法

Question

I have a script for taking data entered into a Price field on my editor and splitting it across a Pounds and Pence field based on the . symbol.

Now I've been asked if I could multiply the Price field by 1.2 and display the result in the Pounds field. The pence field would no longer be needed.

I have no idea if multiplication can even work and especially using decimal points... Can anyone explain how I should rewrite the below?

$('#price1').keyup(function(event) {
    if ($('#price1').val().indexOf('.') != -1){
        $('#pence1').val($('#price1').val().substr($('#price1').val().indexOf('.') + 1, $('#price1').val().lengh));  
        $('#pound1').val($('#price1').val().substr(0, $('#price1').val().indexOf('.')));  
    }else{
        $('#pound1').val($('#price1').val());
    };
});

Answer 1

Some things to remark:

• Your current solution has a spelling mistake for length .

• Don't locate the decimal point. Instead use native JavaScript capabilities to evaluate the input. You can use parseFloat() , Number() or the unary plus operator for that.

• Once you have the numeric value, you can multiply using the * operator. As multiplication will also convert its operands to number, you don't even need the previous advice, although it is still good practice to first do the conversion to number and then do the arithmetic.

• Use the input event instead of the keyup event: input is not always the result of key events (think copy/paste via context menu, drag/drop, other devices...)

Here is the proposed solution:

$('#price1').on("input", function(event) {
    var num = +$('#price1').val(); // convert to number using unary plus operator
    // multiply, format as string with 2 decimals, and convert back to number
    num = +(num * 1.2).toFixed(2)
    $('#pound1').val(num);  // output
});