More on ES6 part 4

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More on ES6

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Built-in Methods

ES6 also introduced new built-in methods to make several tasks easier. Here we will cover the most common ones.

Array Element Finding

The legacy way to find the first element of an array by its value and a rule was the following:

[4, 5, 1, 8, 2, 0].filter(function (x) {
return x > 3;
})[0];Try It Yourself

The new syntax is cleaner and more robust:

[4, 5, 1, 8, 2, 0].find(x => x > 3);Try It Yourself

You can also get the index of the item above by using the findIndex() method:

[4, 5, 1, 8, 2, 0].findIndex(x => x > 3);Try It Yourself

Repeating Strings

Before ES6 the following syntax was the correct way to repeat a string multiple times:

console.log(Array(3 + 1).join("foo")); // foofoofooTry It Yourself

With the new syntax, it becomes:

console.log("foo".repeat(3)); // foofoofooTry It Yourself

Searching Strings

Before ES6 we only used the indexOf() method to find the position of the text in the string. For example:

"SoloLearn".indexOf("Solo") === 0; // true
"SoloLearn".indexOf("Solo") === (4 - "Solo".length); // true
"SoloLearn".indexOf("loLe") !== -1; // true
"SoloLearn".indexOf("olo", 1) !== -1; // true
"SoloLearn".indexOf("olo", 2) !== -1; // falseTry It Yourself

ES6 has replaced this with a version that has cleaner and more simplified syntax:

"SoloLearn".startsWith("Solo", 0); // true
"SoloLearn".endsWith("Solo", 4); // true
"SoloLearn".includes("loLe"); // true
"SoloLearn".includes("olo", 1); // true
"SoloLearn".includes("olo", 2); // falseTry It Yourself

It is always a good practice to refactor your code with the new syntax to learn new things and make your code more understandable.