Javscript data structures and control challenge

javscript-data-structures-and-control-challenge.markdown

Javscript data structures and control challenge

This is from the challenge at the end of the the "javascript data structures and control" section of stream 1

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script.js

// We want to take a paragraph of text and filter out certain parts of it.
// In our case, we’ll go over a profile text and remove all the uninteresting stop words. 
// The steps will involve splitting the text into an array of words. Then iterating over 
// the words and keeping all words except those that are contained in the separate 
// array of stop words. You can start by using the following:
//
// var profile = "I am a web developer developing in html css and javascript";
// var stops = ["i","am","a","and"]; //words to be removed from profile

var profile = "I am a web developer developing in html css and javascript";
var stops = ["i","am","a","and"];

// First 'tokenise' the string. This simply means taking the string and breaking
// it up into smaller parts (sometimes called "tokens"). We choose what character
// we want to split on (called the "delimited"). In our example this is simply a space
var words = profile.split(' ');

// Approach 1: use a separate array and copy the valid words to it
var validWords = [],
    validProfile = "";
for(i = 0; i < words.length; i++) {
  // Note: you might try use here:
  // if(... in ...)
  // but rememeber the 'in' operator is to check
  // if a object has a particular key:
  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/in
  var word = words[i];
  if(stops.indexOf(word.toLowerCase()) === -1) { 
    validWords.push(word);
  } 
}

// Convert the array back into a string by "joining". This is the opposite of "split". 
// We stick all the words back together with a space between each of them.
validProfile = validWords.join(" ");

console.log("Approach 1 result: " + validProfile);

// Approach 2: Use the "filter" built in
// "filter" is a built-in function available on arrays that allows you to create
// new arrays from the original array. You define a function that returns a 
// boolean value. This function is called on every member of the array. If 
// the function returns true, that value is included in the result. If it returns
// false, it is not included.
var validWords = words.filter(function(word) {
  return (stops.indexOf(word.toLowerCase()) === -1);
});
console.log("Approach 2 result: " + validWords);