// String.prototype.includes(substring, startingAt)
'Hello world'.includes('wor') //  true
'Hello world'.includes('hell') //  false, sensible à la casse
'Hello world'.includes('Hello', 1) //  false, on commence à 1

// String.prototype.startsWith(substring, startingAt)
'42, born to code'.startsWith('42') //  true
'42, born to code'.startsWith('foo') //  false
'42, born to code'.startsWith(42, 1) //  false, on commence à 1

// String.prototype.endsWith(substring, startingAt)
'42, born to code'.endsWith('code') //  true
'42, born to code'.endsWith('born') //  false
'42, born to code'.endsWith('code', 5) //  false, on arrete à 5


// Exemple equivalent es5
String.prototype.startsWith = function(substring, startingAt) {
  startingAt = (startingAt) ? startingAt : 0;
  return (this.indexOf(substring) === startingAt);
};