| 2022-09-01

Array.map Explained

    The Array.map() method is a useful feature in JavaScript that can help you loop through an array and create a new array with updated data. Here's how it works:

    const items = ["item1", "item2", "item3", "item4"];
    
    items.map((item) => {
      return `The current item is: ${item}`;
    });
    
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    In this example, we have an array called items with several strings representing different items. We can use the Array.map() method to loop through this array and create a new array with updated data.

    The first parameter of Array.map() is a callback function that is invoked on each iteration of the loop. The first parameter of the callback function is the value of the current item in the array. In our example, we have named this value item, which will hold the contents of the array at the specific iteration index. So, item1 will be the first value, then item2, and so on.

    Using Array.map() is especially useful when we need to create a new array based on data from an existing array. For example, we can create a new array of strings like this:

    const animals = ["cat", "dog", "fish", "bird"];
    const kids = ["Billy", "Lisa", "Trevor", "Tracy"];
    const favoriteAnimals = animals.map((animal, index) => {
      return `${kids[index]}'s favorite animal is ${animal}.`;
    });
    
    javascript

    In this example, we have two arrays: animals and kids. We want to create a new array that includes the name of a kid and their favorite animal. We can achieve this by using the Array.map() method and passing in a callback function with two parameters: the value of the current item in the animals array, and the index of that item.

    We can use the index to extract the corresponding value from the kids array, and return a new string with the description of the animal and the name of the kid. The result will be a new array that includes these updated strings.

    [
      "Billy's favorite animal is cat.",
      "Lisa's favorite animal is dog.",
      "Trevor's favorite animal is fish.",
      "Tracy's favorite animal is bird.",
    ];
    
    javascript

    In summary, the Array.map() method is a powerful tool for working with arrays in JavaScript. By returning a new array with transformed data, you can easily update the contents of an existing array without modifying it directly. This approach helps keep your code clean and readable, and reduces the risk of introducing hard-to-find bugs.


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