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ES series of articles

  • ES6 variable constant (let const)
  • Deconstruction assignment
  • ES5 Array traversal mode
  • ES6 Array traversal mode
  • Extension of arrays
  • Arguments to the ES6 function
  • Extension operators and REST parameters
  • Arrow function
  • Object extension

Extension of regular

Regular expressions are used to match strings, and in ES5 there are three modifiers: I (case insensitive) M (multi-line matching) G (global matching). Es6 has two new modifiers: y(adhesion) and U (Unicode).

Regular expression online test tool

– measure words

character meaning
? Zero or one occurrence (maximum one occurrence)
+ Appear once or more (at least once)
* Zero or more occurrences (any occurrence)
{n} A n time
{n,m} N to m occurrences
{n,} At least n

Border –

character Equivalence class
^ Start with XXX
$ Ended up with XXX
\b Word boundaries
\B Non-word boundary

– Predefined classes

character Equivalence class meaning
. [^\r\n] All characters except carriage returns and newlines
\d [0-9] Numeric characters
\D [^ 0-9] Non-numeric character
\s [\t\n\xOB\f\r] Whitespace characters
\S [^\t\n\xOB\f\r] Non-whitespace character
\w [a-zA-Z_0-9] Word character (alphanumeric underscore)
\W [^a-zA-Z_0-9] Non-word character

Y modifier

The y modifier is similar to the G modifier in that it is a global match, and each subsequent match starts at the position following the last successful match. The difference is that the G modifier works as long as there is a match in the remaining position, while the Y modifier ensures that the match must start at the first remaining position, which is what “bonding” means.

Const STR = 'aaa_aa_A' const reg1 = /a+/g // The remaining const reg2 = /a+/y // the first remaining start matches console.log(reg1.exec(STR)) console.log(reg2.exec(str)) console.log(reg1.exec(str)) // aa console.log(reg2.exec(str)) // null console.log(reg1.exec(str)) console.log(reg2.exec(str))Copy the code

U modifier

// \u0000~\ uFFFF es5 range const STR = '\ ud8442 \uDFB7' console.log(/^\uD842/.test(STR)) // es5 true console.log(/^\uD842/u.test(str)) // es6 false // . Any single character except newline console.log(/^.$/.test(STR)) // false console.log(/^.$/u.test(STR)) // true The console. The log (/ \ u {61} /. The test (' a ')) / / false console. The log (/ \ u {61} / u.t est (' a ')) / / true console. The log (/ 𠮷 {2} /. The test (' 𠮷 𠮷 ')) / / False to the console. The log (/ 𠮷 {2} / u.t est (' 𠮷 𠮷 ')) / / trueCopy the code

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