JavaScript - simplify/shorten code

Question

I have the following function which I would like to simplify with a for loop maybe but don't know how to do it. any help will be much appreciated. Basically, if the field value is 0 or null then my total value (field) should be 0 otherwise if the field value is from 1 until 1000 then the total value becomes 5000. For every 1000 (i.e. 1001 until 2000) my total value should increase by 50 i.e. 5050. This should continue until the field value reaches 200000 and the total is 50000.

function calc56() {
 var56 = parseFloat(document.getElementById('units56').value - 0);
 if (var56 == '' || var56 == 0) {
 document.getElementById('amount56').value = 0;
 }
 else if (var56 < 1000) {
 document.getElementById('amount56').value = 5000;
 }
 else if ((var56 > 1000) && (var56 <= 2000)) {
 document.getElementById('amount56').value = 5050;
 }
 else if ((var56 > 2000) && (var56 <= 3000)) {
 document.getElementById('amount56').value = 5100;
 }
}

Thanks in advance.

• Daniel A. White: I'm voting to close this question as off-topic because it is asking for an improve ment to working code. ask on codereview.stackexchange.com
• Stephan Bijzitter: ˆ- migrate the question to the correct site, please.
• gothical: Few things about your code. If var56 is less than 0 you will still get 1000 and you say 1 to 1000 but your condition is var56 < 1000 which means it will only work to 999 and 1000 will not trigger any of the conditions.
• Stephan Bijzitter: The below zero is a good point

Answer 1

function calc56() {
 var el = document.getElementById('units56'); //reference the dom element
 var val = +el.value; //convert to float
 if (!val) { //if no value, leave untouched
 } else if (val < 0) { //if value is less than 0, make it 0.
 el.value = 0;
 } else { //otherwise, calculate new value
 var mod = Math.floor(val / 1000); //calc how many 1000s fit in the value
 el.value = mod * 50 + 5000; //use at least 5000, and add 50 for every 1000
 }
}

I would suggest you also change the name of the function, as it's not very useful. However, this code right here should be the most efficient you can get while still keeping it readable.

If you need more clarification, feel free to ask in a comment!

• Alexander Elgin: Check my solution (2 tiny functions, 7 lines of code, a live snippet that anyone can check) if you think that your code is the most efficient
• Stephan Bijzitter: Well, since your answer contains more function calls, duplicates a DOM query and is able to trigger a DOM repaint even without changing the value, @AlexanderElgin, I do not have to think long to see my answer is much more efficient ;-)