Detailed explanation of the usage of JavaScript's replace() when passing in a function

This article brings you a detailed explanation of the usage of JavaScript's replace() when passing in the function. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

Basic usage:

Usage when using capturing group:

Requirement: Change the number to the left of the floating point point every three digits Add a comma?

var str = '12000000.11'; var res = str.replace(/(\d)(?=(\d{3})+\.)/g, function(s1, s2) { console.log(arguments) // (\d{3})+ 虽然有+但只算一个捕获组 return s2 + ','; // 替换匹配成功的返回值 }); console.log(res) // 12,000,000.11 /* arguments的值为(匹配成功两次)： ["2", "2", "000", 1, "12000000.11"] ["0", "0", "000", 4, "12000000.11"] 第一项：匹配成功返回的结果（预测断言匹配成功的值不会出现在匹配结果中） 第二项：第一个捕获组对应的值 第三项：第二个捕获组对应的值 第四项：匹配字符串的索引值 第五项：原始字符串 */

Analysis:
?=exp: Prediction assertion, the position where the assertion appears must match exp, otherwise the match fails, and the length will not be occupied after the match is successful.

/(\d)(?=(\d{3}) .)/g performs global matching. The string that successfully matched for the first time is: "2000000."
The second match The successful string is "0000."

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