The usage and difference between substr and substring in JS

Substr and substring in JS are both functions used to intercept strings. The former refers to intercepting a string of specified length starting from a specified position, and the latter refers to intercepting from start to end but not including the end length. The string

substr and substring are both functions for intercepting strings in JavaScript. However, because the usage of the two is very similar, they are often confused. I will introduce it in detail in the article. The usage and difference between the two have a certain reference effect and I hope it will be helpful to everyone.

[Recommended course: JavaScript Tutorial]

substr method

is used to return a from A substring of specified length starting at a specified position. Its syntax is as follows

str.substr(start [, length ])

where str represents the string to be intercepted, start represents the starting position of the required substring, and the default is the first The index of characters is 0, length refers to the number of characters contained in the returned substring

Note: When length is 0 or a negative number, an empty string will be returned

substring method

is used to return the substring located at the specified position in the str object. The syntax is as follows

str.substring(start, end)

means that the method will return a A substring from start to end (excluding end), where start represents the starting position of the substring, the default value is 0, and end refers to the end position of the string

Note: substring The method uses the smaller of start and end as the starting point

Example

 str.substring(0, 3)

is equivalent to

str.substring(3, 0)

If start or end is NaN or a negative number, replace it with 0, where the length of the string is the absolute value of the difference between start and end

Example:

<script>
var str = &#39;abcdefg&#39;
var str1 = str.substring(1,2);
var str2 = str.substr(1,2);
console.log("substring返回的值："+str1); 
console.log("substr返回的值："+str2); 
</script>

Rendering:

It can be seen that the length of the string returned by substring is 1, and the length returned by substr is 2.

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