I have to decompose words into collections of letters in Javascript. Then I need to be able to i) check whether a letter belongs to the collection and ii) to remove letters for this collection progressively.
For example, the word 'cool' would be decomposed into 'c', 'o', 'o', 'l'. If I remove 'o', 'a' and 'l', I should be left with 'c', 'o' only.
What is the proper data structure to achieve this in Javascript?
A string!
var str = 'cool';
To check if a character is in the string:
if(str.indexOf('o') > -1) // the character is in the string
To remove the first occurrence of a character:
str = str.replace('o','');
If you want to modify the string object to provide more "logical" representations of these actions you could do this:
String.prototype.contains = function(char){
return this.indexOf(char) > -1;
};
String.prototype.remove = function(char){
return this.replace(char,'');
};
which you could use like this:
if ('cheese'.contains('che'))
alert('Velviva!');
var str = 'hurt'.remove('r'); // 'hut'
str = 'banana'.remove('n'); // 'baana'
str = 'happy'.remove('c'); // 'happy'
An array! You can get one by simply splitting the string like this:
var arr = "word".split("");
You can use the methods from Array.prototype to manipulate the collection like you said. For example, to remove the character at index 1:
arr.splice(1,1);
To make it a string again:
arr.join('');
If you just want to read a particular character from a string, you can just access its index directly:
var str = "word";
str[1]; // "o"
There are also other string methods you can use to achieve the same result you'd get with an array (see Shmiddty's answer).
JavaScript's object can be used for that, for instance:
var cool = "cool".split(""); // `cool` is an array of single-char strings
var crossIndex = {};
cool.forEach(function(entry) {
crossIndex[entry] = true;
});
Now crossIndex has flags for whether it has a given letter, so:
var letter = "c"; // for instance
if (crossIndex[letter]) {
// It has it
// If you want to remove it:
delete crossIndex[leter];
}
else {
// It doesn't have it
}
if (letter in crossIndex)
Object(which a bit like a dictionary) andArray, from both of which you can build on more complicated collections.