Question:
 

Answer:
Many people have been asking how to do this. Since JavaScript does not have built-in methods for converting numbers to currency-formatted strings, the only option left is to make a function that does it for us — which I have already done for you.

The name of the function is toUSCurrency. It takes a number or string as input and returns a new string representing the original input as US currency. I present it to you in an edit-box so that you can cut and paste it into your own JavaScript programs:

function toUSCurrency (input){ // Make sure input is a string: input += “”; // Keep original copy of input string: var original_input = input; // Strip leading dollar sign if necessary: if (input . charAt (0) == “$”) input = input . substring (1, input . length); else if ( input . substring (0, 2) == “-$” || input . substring (0, 2) == “+$” ) input = input . charAt (0) + input . substring (2, input . length); // Get float value: var amount = parseFloat (input); // Return unmodified input if we weren’t able to convert it: if (isNaN (amount)) return original_input; // Express amount in pennies, rounded to the nearest penny: amount = Math . round (100 * amount); // Prepare to add a US currency prefix: var prefix = “$”; if (amount < 0) { prefix = "-" + prefix; amount = - amount; } // Convert amount to string and pad with leading zeros if necessary: var string; if (amount < 10) string = "00" + amount; else if (amount < 100) string = "0" + amount; else string = "" + amount; // Insert prefix: string = prefix + string; // Insert decimal point before last two digits: string = string . substring (0, string . length - 2) + "." + string . substring (string . length - 2, string . length); // Return formatted currency string: return string;}

By the way, this function was designed to withstand abuse. If the number or string passed in cannot be converted, then a string representing the original, unmodified input is returned instead.

The following form is provided so that you can experiment with the toUSCurrency function and determine if it suits your needs.

Input: Output:

Output = toUSCurrency (Input);

If you like toUSCurrency, please feel free to use it in your own JavaScript programs.