An explanation of regular laziness and greed

This article brings an explanation of regular laziness and greed. I hope it will be helpful to everyone.

exec - > Regular capture

Every time you capture, the default match is performed first. If there is no successful match, The captured result is null; we can capture only if there is matching content;

Captured content format

1. Captured content Is an array. The first item in the array is the content captured by the current regular expression.

Index: The index position where the captured content starts in the string.

Input: The captured original string

  reg = /\d+/ str = 'woshi2016ni2017' res =

var res = reg.exec(str);
console.log(res) // ['2016',index:5,input:'woshi2016ni2017']

2. Characteristics of regular capture

1) Lazy Properties -> Each time exec is executed, only the first matching content is captured. Without any processing, even if multiple captures are performed, the first matching content is still captured.

lastIndex: is the position where the search starts in the string for each regular capture. The default value is 0

2) How to solve laziness Sexuality? Add a modifier "g"

at the end of the regular expression Modifiers: g, i, m

global(g): Global matching

##　ignoreCase(i): Ignore case matching

multiline(m):Multiline matching　

var reg = /\d/g;

var str = 'woshi2016ni2017';

console.log(reg.lastIndex)

console.log(reg.exec(str))

##　

var reg = /\d+/g;var str = 'aswofde2015xsewde2016awdefer2017';var ary = [];var res = reg.exec(str);while(res){
            ary.push(res[0])
            res = reg.exec(str);
        }
        console.log(ary)//[2015,2016,2017]

　5) How to solve the greedy nature of the regular pattern -> after the quantifier metacharacter add one? Just

var reg = /\d+?/g;var str = 'aswofde2015xsewde2016awdefer2017';
        console.log(reg.exec(str));

　Place A

metacharacter followed by represents 0-1 occurrences of /\d?/ -> The number may or may not appear Putting it after the

quantifier is greedy when canceling the capture 3. The match method in the string -> Match everything with the regular expression The characters of

are obtained

var reg = /\d+?/g;var str = 'aswofde2015xsewde2016awdefer2017';var ary = str.match(reg);//[2,0,1,5,2,0,1,6,2,0,1,7]

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