索引

• Notes

  1. js创建正则表达式的两种方式
  2. js正则匹配方式（1）
  3. 字符集合
  4. 重复匹配
  5. 分组（子表达式）
  6. js正则匹配方式（2）
  7. The Date class
  8. 匹配整个字符串
  9. Choice patterns
  10. 正则匹配的机制
  11. 回溯Backtracking
  12. Replace
  13. 贪婪匹配Greed
  14. 动态构建正则表达式
  15. Search
  16. The lastIndex property
  17. 遍历匹配项
  18. 解析INI文件
  19. 国际字符

• Exercise

  1. Regexp golf
  2. Quoting style
  3. Numbers again

let re1 = new RegExp("abc");

let re2 = /abc/;

console.log(/abc/.test("abcde"));

// → true

console.log(/abc/.test("abxde"));

// → false

let notBinary = /[^01]/;

console.log(notBinary.test("1100100010100110"));

// → false

console.log(notBinary.test("1100100010200110"));

// → true

console.log(/'\d+'/.test("'123'"));

// → true

console.log(/'\d+'/.test("''"));

// → false

console.log(/'\d*'/.test("'123'"));

// → true

console.log(/'\d*'/.test("''"));

// → true

let neighbor = /neighbou?r/;

console.log(neighbor.test("neighbour"));

// → true

console.log(neighbor.test("neighbor"));

// → true

let dateTime = /\d{1,2}-\d{1,2}-\d{4} \d{1,2}:\d{2}/;

console.log(dateTime.test("1-30-2003 8:45"));

// → true

let cartoonCrying = /boo+(hoo+)+/i;

console.log(cartoonCrying.test("Boohoooohoohooo"));

// → true

let match = /\d+/.exec("one two 100");

console.log(match);

// → ["100"]

console.log(match.index);

// → 8

console.log("one two 100".match(/\d+/));

// → ["100"]

let quotedText = /'([^']*)'/;

console.log(quotedText.exec("she said 'hello'"));

// → ["'hello'", "hello"]

console.log(/bad(ly)?/.exec("bad"));

// → ["bad", undefined]

console.log(/(\d)+/.exec("123"));

// → ["123", "3"]

console.log(new Date());

// → Sat Sep 01 2018 13:54:43 GMT+0800 (中国标准时间)

console.log(new Date(2009, 11, 9));

// → Wed Dec 09 2009 00:00:00 GMT+0800 (中国标准时间)

console.log(new Date(2009, 11, 9, 12, 59, 59, 999));

// → Wed Dec 09 2009 12:59:59 GMT+0800 (中国标准时间)

console.log(new Date(1997, 10, 19).getTime());

// → 879868800000

console.log(new Date(1387407600000));

// → Thu Dec 19 2013 07:00:00 GMT+0800 (中国标准时间)

console.log(new Date().getTime());

// → 1535781283593

console.log(Date.now());

// → 1535781283593

"use strict";

function getDate(string) {

  let [_, month, day, year] =

    /(\d{1,2})-(\d{1,2})-(\d{4})/.exec(string);

  return new Date(year, month - 1, day);

}

console.log(getDate("1-30-2003"));

// → Thu Jan 30 2003 00:00:00 GMT+0100 (CET)

console.log(/cat/.test("concatenate"));

// → true

console.log(/\bcat\b/.test("concatenate"));

// → false

console.log(/\bcat\b/.test("xx cat xx"));

// → true

let animalCount = /\b\d+ (pig|cow|chicken)s?\b/;

console.log(animalCount.test("15 pigs"));

// → true

console.log(animalCount.test("15 pigchickens"));

// → false

/**

 * 模拟用正则\b\d+ (pig|cow|chicken)s?\b

 * 匹配"the 3 pigs"

 */

const str = "the 3 pigs";

function simulateRegex(str, start) {

    const digits = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];

    // 逐个字符尝试匹配，直到找到一个匹配项或者到达字符串尾结束

    for(let currentPosition = start; currentPosition != str.length; ++currentPosition) {

        let tempPosition = currentPosition;

        if(tempPosition == 0 || str[tempPosition - 1] == " ") {} else continue;

        // 匹配单词边界通过，前面是标点也是可以的。。

        if(!str[tempPosition++] in digits) continue;

        // 至少匹配一个数字通过

        while(str[tempPosition] in digits) {

            tempPosition++;

            // 尝试继续匹配数字

        }

        if(str[tempPosition++] != " ") continue;

        // 匹配一个空格通过

        let tempWord;

        if(str.slice(tempPosition, tempPosition + "pig".length) === (tempWord = "pig") ||

            str.slice(tempPosition, tempPosition + "cow".length) === (tempWord = "cow") ||

            str.slice(tempPosition, tempPosition + "chicken".length) === (tempWord = "chicken")) {

            tempPosition += tempWord.length;

        } else {

            continue;

        }

        // 单词匹配成功

        if(str[tempPosition] == "s") tempPosition++;

        // 有没s都可以

        if(tempPosition == str.length || str[tempPosition] == " ") {

            // 最后的单词边界

            let match = [str.slice(currentPosition, tempPosition + 1)];

            return match;

        }

    }

    return null;

}

let match = simulateRegex(str, 4);

console.log(match);

// → ["3 pigs"]

console.log("papa".replace("p", "m"));

// → mapa

console.log("Borobudur".replace(/[ou]/, "a"));

// → Barobudur

console.log("Borobudur".replace(/[ou]/g, "a")); // g代表global全部

// → Barabadar

console.log(

  "Liskov, Barbara\nMcCarthy, John\nWadler, Philip"

    .replace(/(\w+), (\w+)/g, "$2 $1"));

// → Barbara Liskov

//   John McCarthy

//   Philip Wadler

"hello, word, every, one".replace(/(\w+),/g, "$1 "); // “$+数字”引用匹配中的分组

// → "hello  word  every  one"

"hello, word, every, one".replace(/one/g, "$& $&"); // “$&”引用整个匹配

// → "hello, word, every, one one"

"hello, word, every, one".replace(/(\w+),/g, str => str.toUpperCase());

// → "HELLO, WORD, EVERY, one"

let stock = "1 lemon, 2 cabbages, and 101 eggs";

function minusOne(match, amount, unit) {

  amount = Number(amount) - 1;

  if (amount == 1) { // only one left, remove the 's'

    unit = unit.slice(0, unit.length - 1);

  } else if (amount == 0) {

    amount = "no";

  }

  return amount + " " + unit;

}

console.log(stock.replace(/(\d+) (\w+)/g, minusOne));

// → no lemon, 1 cabbage, and 100 eggs

function stripComments(code) {

  return code.replace(/\/\/.*|\/\*[^]*\*\//g, "");

}

console.log(stripComments("1 + /* 2 */3"));

// → 1 + 3

console.log(stripComments("x = 10;// ten!"));

// → x = 10;

console.log(stripComments("1 /* a */+/* b */ 1"));

// → 1  1

function stripComments(code) {

  return code.replace(/\/\/.*|\/\*[^]*?\*\//g, "");

}

console.log(stripComments("1 /* a */+/* b */ 1"));

// → 1 + 1

let name = "harry";

let text = "Harry is a suspicious character.";

let regexp = new RegExp("\\b(" + name + ")\\b", "gi");

console.log(text.replace(regexp, "_$1_"));

// → _Harry_ is a suspicious character.

let name = "dea+hl[]rd";

let text = "This dea+hl[]rd guy is super annoying.";

let escaped = name.replace(/[\\[.+*?(){|^$]/g, "\\$&");

// escaped → "dea\+hl\[]rd"

let regexp = new RegExp("\\b" + escaped + "\\b", "gi");

console.log(text.replace(regexp, "_$&_"));

// → This _dea+hl[]rd_ guy is super annoying.

console.log("  word".search(/\S/));

// → 2

console.log("    ".search(/\S/));

// → -1

let pattern = /y/g;

pattern.lastIndex = 3;

let match = pattern.exec("xyzzy");

console.log(match.index);

// → 4

console.log(pattern.lastIndex);

// → 5

let global = /abc/g;

console.log(global.exec("xyz abc"));

// → ["abc"]

let sticky = /abc/y;

console.log(sticky.exec("xyz abc"));

// → null

let global = /abc/g;

global.lastIndex = 6; // 从c开始向后搜索匹配

console.log(global.exec("xyz abc"));

// → null

let sticky = /abc/y;

sticky.lastIndex = 4; // 从a开始匹配

console.log(sticky.exec("xyz abc"));

// → ["abc"]

let digit = /\d/g;

console.log(digit.exec("here it is: 1"));

// → ["1"]

console.log(digit.exec("and now: 1"));

// → null

console.log("Banana".match(/an/g));

// → ["an", "an"]

console.log(/an/g.exec("Banana"));

// → ["an", index: 1, input: "Banana", groups: undefined]

// global改变了match的行为，本来上述两个

// 输出应该相同的（等价操作），而且["an", "an"]

// 后者本应该是子表达式匹配的字符串，前者的子集

let input = "A string with 3 numbers in it... 42 and 88.";

let number = /\b\d+\b/g;

let match;

while (match = number.exec(input)) {

  console.log("Found", match[0], "at", match.index);

}

// → Found 3 at 14

//   Found 42 at 33

//   Found 88 at 40

function parseINI(string) {

    // Start with an object to hold the top-level fields

    let result = {};

    let section = result;

    string.split(/\r?\n/).forEach(line => {

        let match;

        if(match = line.match(/^(\w+)=(.*)$/)) {

            section[match[1]] = match[2];

        } else if(match = line.match(/^\[(.*)\]$/)) {

            section = result[match[1]] = {};

        } else if(!/^\s*(;.*)?$/.test(line)) {

            throw new Error("Line '" + line + "' is not valid.");

        }

    });

    return result;

}

console.log(parseINI(`

searchengine=https://duckduckgo.com/?q=$1

spitefulness=9.7

; comments are preceded by a semicolon...

; each section concerns an individual enemy

[larry]

fullname=Larry Doe

type=kindergarten bully

website=http://www.geocities.com/CapeCanaveral/11451

[davaeorn]

fullname=Davaeorn

type=evil wizard

outputdir=/home/marijn/enemies/davaeorn`));

// → davaeorn:  { fullname: "Davaeorn", type: "evil wizard", outputdir: "/home/marijn/enemies/davaeorn" }​

// larry:  { fullname: "Larry Doe", type: "kindergarten bully", website: "http://www.geocities.com/CapeCanaveral/11451" }​

// searchengine: "https://duckduckgo.com/?q=$1"​

// spitefulness: "9.7"

console.log(/												


																
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