Highlights of JavaScript — Array Loops and Strings

Highlights of JavaScript — Array Loops and Strings

To learn JavaScript, we must learn the basics.

To learn JavaScript, we must learn the basics.

In this article, we’ll look at the most basic parts of the JavaScript language.

Looping Through an Array

We can loop through an array with by using the length property of an array for the ending condition.

For example, we can write:

let matchFound = false;
for (let i = 0; i < cleanestCities.length; i++) {
  if (city === cleanestCities[i]) {
    matchFound = true;
    console.log("It's one of the cleanest cities");
  }
}

We get the length property of the cleanestCities array for the ending condition.

We loop from 0 to cleanestCities.length — 1 . This way, we loop through the items from start to end without setting comparing a fixed number value for the ending condition.

If we want to stop a loop early, we can use the break keyword.

For example, we can write:

for (let i = 0; i < cleanestCities.length; i++) {
  if (city === cleanestCities[i]) {
    console.log("It's one of the cleanest cities");
    break;
  }
}

If city is equal to clesnestCities[i] , then we end the loop with break .

We can nest loops in our code. For example, we can write:

let firstNames = ['james', 'mary', 'alex'];
let lastNames = ['jones', 'wong', 'green'];
let fullNames = [];
for (let i = 0; i < firstNames.length; i++) {
  for (let j = 0; j < lastNames.length; j++) {
    fullNames.push(`${firstNames[i]} ${ lastNames[j]}`);
  }
}

We have a for loop inside another for loop.

The outer loop loops through the firstNames array.

In each iteration, the inner loop is run to loop through the lastNames array.

And inside the inner loop, we push the combination of firstNames[i] and lastNames[j] into the fullNames array.

The result is all the combinations of firstNames and lastNames entries added to the fullNames array.

We can have as many levels of nesting as we like. However, the more nesting we have, the harder the code is to read.

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