Question

I have a string

strdata = "<mymarkup><P>Hello world!</P>"

in an array. So for strata[1][1] that contains the above value. How can I detect the < characters with the substring function?

For example:

if (strata[1][1].substring(0,9) = "<mymarkup>") { 
  // etc...

Answer 1

If you only ever have to check against the same string. E.g. “<mymarkup>” its best to use maerics snippet.

However if you have to check against a lot of different strings it will get cumbersome. Here is a reusable example to check if a string starts with a given prefix.

Functional style:

function startsWith(str, starts){
  return str.length >= starts.length && str.substring(0, starts.length) === starts;
 }

if(startsWith(strata[1][1], '<mymarkup>')){ 
 // do something
}

Object-oriented style

String.prototype.startsWith = function(starts){
    return this.length >= starts.length && this.substring(0, starts.length) === starts;
};

if(strata[1][1].startsWith('<mymarkup>')){ 
// do something
}