Ce tutoriel vous guidera l'article JavaScript comment ma?triser des objets tableau JavaScript avec des comp?tences JavaScript avance par instructions ?tape par ?tape , simple code source JavaScript et une documentation tr?s d?taill?e Dans ce tutoriel, JavaScript, vous pouvez en apprendre davantage sur forEach, filter, every, some, map, reduce
des m?thodes pour manipuler des objets tableau JavaScript mieux.
- Demo
- Agrandir
- Recharger
- New window
Gratuit iPage hébergement Web pour la première année MOMENT
Si vous êtes toujours à la recherche d'un fournisseur d'hébergement Web fiable avec des tarifs abordables, pourquoi vous ne prenez pas un peu de temps pour essayer iPage, seulement avec $1.89/month, inclus $500+ Crédits supplémentaires gratuites pour le paiement de 24 mois ($45)?
Plus de 1.000.000 de clients + existisng peuvent pas avoir tort, vraiment vous n'êtes pas aussi! Plus important encore, lorsque vous enregistrez l'hébergement web à iPage grâce à notre lien, nous allons être heureux de renvoyer un plein remboursement. C'est génial! Vous devriez essayer iPage hébergement web GRATUITEMENT maintenant! Et contactez-nous pour tout ce que vous devez savoir sur iPage.
Till recently I always used a for-loop when I had to iterate over an array in JavaScript. For example:
var myArray = [1, 2, 3, 4];
for (var i = 0; i < myArray.length; i++) {
console.log(myArray[i]);
}
However, with ECMAScript 5 the Array object itself got some methods for iteration purposes. With those methods you often can write cleaner code than by using a for-loop. Let’s have a (short) look at those methods. For details, please follow the provided links.
forEach
The forEach() method calls the provided function for each array element. Using forEach(), we can rewrite the example from above to:
var myArray = [1, 2, 3, 4];
myArray.forEach(function (element) {
console.log(element);
});
filter
The filter() method applies the provided filter function to each array element and returns a new array with all elements for which the filter function returned a true value.
For example, to get only the even numbers of an array we could write the following code:
var myArray = [1, 2, 3, 4];
var evenNumbers = myArray.filter(function (x) {
return x % 2 == 0;
});
// evenNumbers is [2, 4]
every & some
The every() and some() methods are similar: whereas the every() method only returns true if the provided testing function returns a true value for each array element, the some() method returns true if there is at least one array element for which the testing function returns a true value. You can see the difference in this example:
var oddNumbers = [1, 3, 5, 7];
var mixedNumbers = [1, 2, 3, 4];
var evenNumbers = [2, 4, 6, 8];
oddNumbers.every(isEven); // returns false
oddNumbers.some(isEven); // returns false
mixedNumbers.every(isEven); // returns false
mixedNumbers.some(isEven); // returns true
evenNumbers.every(isEven); // returns true
evenNumbers.some(isEven); // returns true
function isEven(x) {
return x % 2 == 0;
}
map
The map() method applies the provided function to each array element and returns an array with the results.
For example, to square all values of an array we can do the following:
var myArray = [1, 2, 3, 4];
var squared = myArray.map(function (x) {
return x * x;
});
// squared is [1, 4, 9, 16]
reduce & reduceRight
The reduce() and reduceRight() methods reduce an array step-by-step to a single value by using the provided function and an optional initial value. It works in the following way: the first two array elements (or the initial value and the first array element) are passed as parameters to the provided function. The result of this function call plus the next array element are then used as new parameters for the function. And so on, until there are no more array elements left.
The difference between reduce() and reduceRight() is that reduce() iterates over the array from left-to-right whereas reduceRight() iterates in the opposite direction, from right-to-left.
Here is a simple example to calculate the sum of the values of an array:
var myArray = [1, 2, 3, 4];
var initialValue = 10;
myArray.reduce(add); // performs 1 + 2 + 3 + 4 and returns 10
myArray.reduceRight(add); // performs 4 + 3 + 2 + 1 and returns 10
myArray.reduce(add, initialValue); // performs 10 + 1 + 2 + 3 + 4 and returns 20
myArray.reduceRight(add, initialValue); // performs 10 + 4 + 3 + 2 + 1 and returns 20
function add(x, y) {
return x + y;
}
That’s it. I hope I could give you an overview over the available iteration possibilities in JavaScript. Happy coding!
Update 2011-04-02: I found a site by Microsoft where you can test those methods in your browser: ECMAScript 5 Arrays
- Sent (0)
- Nouveau
Save up to 630$ when buy new iPhone 15
GateIO.gomymobi.com
Free Airdrops to Claim, Share Up to $150,000 per Project
https://tooly.win
Open tool hub for free to use by any one for every one with hundreds of tools
chatGPTaz.com, chatGPT4.win, chatGPT2.fun, re-chatGPT.com
Talk to ChatGPT by your mother language
Dall-E-OpenAI.com
Generate creative images automatically with AI
AIVideo-App.com
Render creative video automatically with AI