Get the highest and lowest values of a certain attribute in jQuery or Javascript

Question

I have the following divs:

test
test


        
      

Answer 1

First you need to create an array containing all the id values, then use Math to get the highest/lowest:

var ids = $(".maindiv[id]").map(function() {
    return parseInt(this.id, 10);
}).get();

var highest = Math.max.apply(Math, ids);
var lowest = Math.min.apply(Math, ids);

Example fiddle

Note the [id] attribute selector is required, otherwise 0 is assumed for the missing value.