concat(), repeat(), slice() and all "searchString" based String prototype methods (#13)

[calluw]

PR for implementation of some of the prototype methods on the String object:

• String.prototype.concat ( ...args )
• String.prototype.endsWith ( searchString [ , endPosition ] )
• String.prototype.includes ( searchString [ , position ] )
• String.prototype.indexOf ( searchString [ , position ] )
• String.prototype.lastIndexOf ( searchString [ , position ] )
• String.prototype.repeat ( count )
• String.prototype.slice ( start, end )
• String.prototype.startsWith ( searchString [ , position ] )

The methods which return string return string values not string objects. Currently in Boa these methods are only available on String objects created directly (via new String(...)), not string literals/values.

This will move the concat, repeat, slice, endsWith, includes, indexOf, lastIndexOf and startsWith entries on issue #13 to done.

Example usage:

let a = new String("Hello ");
let b = a.concat("world!");
b;

Gives:

[src/bin/bin.rs:7] exec(buffer) = "Hello world!"

Test JS:

let a  = new String("Hello world!");
console.log(a.indexOf("o"));
console.log(a.indexOf("warld"));
console.log(a.indexOf("ello", 3));
console.log(a.lastIndexOf("o"));
console.log(a.lastIndexOf("hillo"));
console.log(a.endsWith("orld!"));
console.log(a.endsWith("orld", 11)) // Len - 1
console.log(a.startsWith("Hell"));
console.log(a.startsWith("ell", 1));
console.log(a.startsWith("hell"));
console.log(a.includes("o w"));
console.log(a.includes("o w"), 10);
console.log(a.includes("war"));

Expect output:

22:51:18: 4
22:51:18: -1
22:51:18: -1
22:51:18: 7
22:51:18: -1
22:51:18: true
22:51:18: true
22:51:18: true
22:51:18: true
22:51:18: false
22:55:33: true
22:55:33: false
22:55:33: false

[calluw]

Added all "searchString" based string methods to this pull request as all related to same issue (#13).

[jasonwilliams]

Sorry @CallumQuick there's some conflicts from merging the other PR

[calluw]

@jasonwilliams: merge conflicts have been resolved, please would you be able to take a look.