JavaScript generates simple arithmetic sequence

How does JavaScript generate a simple arithmetic sequence? This article will share with you how to use for loop to implement js to generate a simple arithmetic sequence. Please refer to this article for specific implementation methods.

The question is very simple, the easiest way is to use a for loop

let arr = []
for (let i = 0; i < b - a + 1; i++) {
 arr.push(i + a)
}
return arr

Advanced

When I think about it later, I feel that the previous method is a bit stupid , and then came up with these methods

Array gaps

join() and toString() will treat gaps as undefined (string form):

// 拼接 > 分割 > map
Array(b - a + 1).join(' ').split(' ').map((e, i) => a + i)
// 转字符串 > 分割 > map
Array(b - a + 1).toString().split(',').map((e, i) => a + i)

Use the Array.from method to achieve:

// 空数组转真数组
Array.from(Array(b - a + 1)).map((e, i) => a + i)
// 类似数组的对象转数组
Array.from({ length: b - a + 1 }).map((e, i) => a + i)
Array.from({ length: b - a + 1 }, (e, i) => a + i)

The expansion operator of ES6 can also help us accomplish this more conveniently

[...Array(b - a + 1)].map((e, i) => a + i)
fill()、entries()、keys()方法也不会忽略空位
Array(b - a + 1).fill(' ').map((e, i) => a + i)
[...Array(b - a + 1).entries()].map(e => e[0] + a)
[...Array(b - a + 1).keys()].map(e => e + a)

There are other ways to accomplish this , such as findIndex(), find(), for...of, etc. These methods are not simple enough to implement, so there is no need to go into details.

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