Question

Say I have a JS array like so…

var newArray = [20,182,757,85,433,209,57,828,635];

And I want to use this data to create a bar graph, where the height of the highest bar would == 100.
So, the 828 value bar needs to be set to 100, and the rest of the bars need to be calculated relative to that, and also to the closest integer. I am not sure how to go about this?

Is there a way to create a new array from the one above using a loop? Then I can use the new array?

Answer 1

First, calculate the max value:

var max = Math.max.apply(Math, newArray.map(Math.abs));
// will do `Math.max(300, 20, 182, ...)`
// if `newArray` is `[-300, 20, 182]`

Then, divide each element by that value, do it times 100, and round it down so that the highest value becomes 100:

var normalized = newArray.map(function(v) {
  return Math.round(v / max * 100);
});

.map is essentially a loop, but the loop is done internally so you can write cleaner code. Do note it’s ES5, so you need a shim for older browsers.