Since ES6 has released, we have discussed the interesting features in our site earlier in the ECMAScript 6 tag. ES 6 release contains lots beautiful features like arrow functions, template literals, destructuring, default parameters, etc.
Now, its time experiment and explore es-next – ECMAScript 2016 / ES7 🙂
I shall make a separate post on this name convention of the release later. Now let’s stick with discussion of features.
Ecma Technical Committee 39 governs the ECMA specification. They follow certain stages to handle the proposals, starts from stage 0 to stage 4. The proposals which reached the stage 4 are the finished proposals. ES7 included support for a new exponentiation operator and adds a new method to Array.prototype called includes.
Let’s discuss the following two features in this post:
- Array.prototype.includes
- Exponentiation operator
Array.prototype.includes
The formal syntax of includes is
Array.prototype.includes ( searchElement [ , fromIndex ] )
where fromIndex is optional.
includes compare searchElement to the elements of the array, in ascending order, using the SameValueZero algorithm, and if found at any position, returns true; otherwise, false is returned.
The optional second argument fromIndex defaults to 0 (i.e. the whole array is searched). If it is greater than or equal to the length of the array, false is returned, i.e. the array will not be searched. If it is negative, it is used as the offset from the end of the array to compute fromIndex. If the computed index is less than 0, the whole array will be searched.
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| // ES 7 | |
| var fruits = ['mango', 'jack fruit', 'banana' ] | |
| fruits.includes('mango') // true | |
| fruits.includes('orange') // false | |
| // Earlier | |
| var fruits = ['mango', 'jack fruit', 'banana' ] | |
| fruits.indexOf('banana') // returns 2 – index of the array | |
| fruits.indexOf('orange') // return -1 means value is not available in array |
Earlier, I have used indexOf to check whether the particular element is present in the array or not. Now, using includes we can directly validate the same in conditional loops.
The includes function is intentionally generic; it does not require that its this value be an Array object. Therefore it can be transferred to other kinds of objects for use as a method.
The includes method intentionally differs from the similar indexOf method in two ways. First, it uses the SameValueZero algorithm, instead of Strict Equality Comparison, allowing it to detect NaN array elements. Second, it does not skip missing array elements, instead of treating them as undefined.
Examples:
assert([1, 2, 3].includes(2) === true); assert([1, 2, 3].includes(4) === false); assert([1, 2, NaN].includes(NaN) === true); assert([1, 2, -0].includes(+0) === true); assert([1, 2, +0].includes(-0) === true); assert(["a", "b", "c"].includes("a") === true); assert(["a", "b", "c"].includes("a", 1) === false);
Exponentiation operator
ECMAScript 2016 introduced the exponentiation operator, **.
We already have the operator of addition +, subtraction -, multiplication *, division /. Now its time to experiment the exponentiation operator **.
It operates similarly to Math.pow()
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| // Math.pow (x, y) | |
| Math.pow(2,3) // 8 | |
| 2 ** 3 | |
| // 8 | |
| // where first digit is base and second digit is exponent | |
| var square = 5 ** 2; | |
| console.log(square) // 25 | |
| var cube = 5 ** 3; | |
| console.log(cube) // 125 |
Experiment the above new features, and let me know your feedback on the comment section.
Happy Coding!
Efficient User 