Evaluation maths expressions in JavaScript strings

I have two text boxes on my Form. One is txtNumberOfTablets and the other one is txtTotalQuantity.

I have a HiddenField and I am setting its value in code behind file on page load.

hdfMedicationDosage = "2/3/4开发者_Go百科";

What I want is, whatever user enters to txtNumberOfTablets textbox, should be multiplied with hdfMedicationDosage value when focus is out of txtNumberOfTablets.

For example txtNumberOfTablets contains value 2, and focus is out of txtNumberOfTablets, then that txtTotalQuantity will have a value 2*2/3*2/4*2 i.e.4/6/8

I want to achieve this in JavaScript.

You should create a function that takes the string value in hdfMedicationDosage and uses the string.split() method to get an array of the numbers as strings. Then just iterate through the array and convert each string using Number before doing each multiplication. You can then concatenate the values back together as strings to populate txtTotalQuantity.

You can see this fiddle for a way to do this.

$(document).ready(function(){
    var theValue = "2/3/4", multiplier = '2', newArray=[], valArray;

    valArray = theValue.split('/');

    for(var i=0;i<valArray.length;i++){
        newArray.push(valArray[i] * multiplier);
    }

    var newValue = newArray.join('/');

    $("#result").text(newValue);
});