String split 返回一个元素比预期多的数组（空元素）

Question

I don't understand this behaviour:

var string = 'a,b,c,d,e:10.';
var array = string.split ('.');

I expect this:

console.log (array); // ['a,b,c,d,e:10']
console.log (array.length); // 1

but I get this:

console.log (array); // ['a,b,c,d,e:10', '']
console.log (array.length); // 2

Why two elements are returned instead of one? How does split work?

Is there another way to do this?

Answer 1

You could add a filter to exclude the empty string.

var string = 'a,b,c,d,e:10.';
var array = string.split ('.').filter(function(el) {return el.length != 0});

Answer 2

一个稍微简单的@xdazz 版本，用于排除空字符串（使用ES6 箭头函数）：

var array = string.split('.').filter(x => x);

Answer 3

This is the correct and expected behavior. Given that you've included the separator in the string, the split function (simplified) takes the part to the left of the separator ("a,b,c,d,e:10") as the first element and the part to the rest of the separator (an empty string) as the second element.

If you're really curious about how split() works, you can check out pages 148 and 149 of the ECMA spec (ECMA 262) at http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-262.pdf

Answer 4

Use String.split() method with Array.filter() method.

 var string = 'a,b,c,d,e:10.'; var array = string.split ('.').filter(item => item); console.log(array); // [a,b,c,d,e:10] console.log (array.length); // 1

Answer 5

https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/String/split

trim the trailing period first

'a,b,c,d,e:10.'.replace(/\.$/g,''); // gives "a,b,c,d,e:10"

then split the string

var array = 'a,b,c,d,e:10.'.replace(/\.$/g,'').split('.');

console.log (array.length); // 1

Answer 6

That's because the string ends with the . character - the second item of the array is empty.

If the string won't contain . at all, you will have the desired one item array.

The split() method works like this as far as I can explain in simple words:

1. Look for the given string to split by in the given string. If not found, return one item array with the whole string.
2. If found, iterate over the given string taking the characters between each two occurrences of the string to split by.
3. In case the given string starts with the string to split by, the first item of the result array will be empty.
4. In case the given string ends with the string to split by, the last item of the result array will be empty.

It's explained more technically here , it's pretty much the same for all browsers.

Answer 7

so; [String.prototype] split(separator, limit) return to the normal limit parameter is empty.

"".split(",") // [""]

"a,b,c.".split(".", 1) // ["a,b,c"]

If you could not have done this too, without limit parameter. I think this is a normal operation...

Answer 8

According to MDN web docs :

Note: When the string is empty, split() returns an array containing one empty string, rather than an empty array. If the string and separator are both empty strings, an empty array is returned.

const myString = '';
const splits = myString.split();

console.log(splits); 

// ↪ [""]

Answer 9

Well, split does what it is made to do, it splits your string. Just that the second part of the split is empty.

Answer 10

Because your string is composed of 2 part :

1 : a,b,c,d,e:10

2 : empty

If you try without the dot at the end :

var string = 'a,b,c:10';
var array = string.split ('.');

output is :

["a,b,c:10"]

Answer 11

You have a string with one "." in it and when you use string.split('.') you receive array containing first element with the string content before "." character and the second element with the content of the string after the "." - which is in this case empty string.

So, this behavior is normal. What did you want to achieve by using this string.split?

Answer 12

try this

javascript gives two arrays by split function, then

var Val = "abc@gmail.com";
var mail = Val.split('@');

if(mail[0] && mail[1])  {   alert('valid'); }
else    {   alert('Enter valid email id');  valid=0;    }

if both array contains length greater than 0 then condition will true