There are many ways to traverse arrays in JavaScript, and the choice depends on the specific needs. ① Use for loops to be suitable for scenarios where full control of the loop process (such as accessing indexes, reverse traversal or jumping out in the middle), with strong syntax compatibility but slightly cumbersome; ② The forEach method is suitable for performing operations on each element without requiring mid-exit, with clearer and concise syntax but does not support break; ③ For...of loops are used for scenarios that only focus on values, are concise and intuitive and support break and continue, but cannot directly obtain indexes; ④ map and filter are more suitable for generating new arrays, where maps are used for data conversion and filters are used for conditional filtering. Both are usually used for data processing rather than just traversal execution side effects.
Iterating through arrays in JavaScript is a basic but commonly used operation. The most direct way is to use for loop, but depending on the specific scenario, there are more concise or more appropriate ways.
Using for loops is the most basic way
If you need to have full control over the loop process, such as accessing indexes, backtracking, or jumping out of the loop in the middle, then a traditional for loop is a safe choice:
const arr = ['apple', 'banana', 'orange'];
for (let i = 0; i < arr.length; i ) {
console.log(arr[i]);
}The advantage of this method is that it has good compatibility and can be used in almost all environments. But the disadvantage is that it is a bit cumbersome to write, especially when there is no need for indexing.
forEach is a more modern way of writing
When you only need to perform an operation on each element in the array and do not need to jump out of the loop in the middle, you can use forEach method:
arr.forEach(function(item) {
console.log(item);
});Or write more concisely with the arrow function:
arr.forEach(item => console.log(item));
-
breakdoes not support, and cannot exit midway - Clearer syntax, suitable for most scenarios that "process every element"
for...of traversal values, not caring about indexes
If you only care about the values ??in the array and don't need indexes, you can use for...of loop:
for (const item of arr) {
console.log(item);
}- Concise and intuitive
- Support
breakandcontinue - Can't get the index directly (if necessary, you have to maintain it yourself)
map and filter are more suitable for generating new arrays
Although they are not specifically used for "traversal", they are very useful when dealing with data transformations or filtering:
-
map: Map each element into a new value and return a new array -
filter: filter out some elements according to the conditions and return a new array
Example:
const numbers = [1, 2, 3]; const doubled = numbers.map(n => n * 2); // [2, 4, 6] const even = numbers.filter(n => n % 2 === 0); // [2]
These methods are often used in the data processing stage rather than simply "printing" or "executing side effects".
Basically these common ways. Each method has applicable scenarios. Which one you choose depends on whether you need an index, whether you want to exit midway, whether you want to generate a new array, etc.
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