JavaScript - 文本格式化

字符串

字符串字面表达

'foo'
"bar"

Hexadecimal转义序列

'\xA9' // "©"

Unicode转义序列

'\u00A9' // "©"

Unicode code point escape

'\u{2F804}'

// the same with simple Unicode escapes
'\uD87E\uDC04'

字符串对象 

字符串对象是对原始字符串数据类型的封装

const foo = new String('foo'); // Creates a String object
console.log(foo); // Displays: [String: 'foo']
typeof foo; // Returns 'object'

const firstString = '2 + 2'; // Creates a string literal value
const secondString = new String('2 + 2'); // Creates a String object
eval(firstString); // Returns the number 4
eval(secondString); // Returns the string "2 + 2"

const hello = 'Hello, World!';
const helloLength = hello.length;
hello[0] = 'L'; // This has no effect, because strings are immutable
hello[0]; // This returns "H"

字符串对象的方法

charAt, charCodeAt, codePointAt	返回索引指定位置的字符或者字符编码
indexOf, lastIndexOf	返回指定子字符串初次出现的位置，或者最后一次出现的位置
startsWith, endsWith, includes	判断是否以某指定文字起始、结尾、或者包含某指定文字
concat	连接两个字符串，以新字符串返回
fromCharCode, fromCodePoint	基于Unicode值创建字符串
split	依据指定的分割符，将字符串分割写入数组
slice	将字符串切割为片段，返回新字符串
subString, subStr	依据指定索引返回子字符串
match, replace, search	同正则表达式一起工作
toLowerCase, toUpperCase	大小写转换
normalize	返回字符串的Unicode Normalization Form
repeat	取得该字符串指定重复次数的字符串
trim	除去字符串起始和结尾的空白

 

 

 

 

 

 

 

 

 

 

 

 

 

多行模板文字

模板文字允许表达式嵌套在其中，模板文字使用回剔符号包围(``)

多行

console.log('string text line 1\n\
string text line 2');
// "string text line 1
// string text line 2"

console.log(`string text line 1
string text line 2`);
// "string text line 1
// string text line 2"

嵌套表达式

const five = 5;
const ten = 10;
console.log('Fifteen is ' + (five + ten) + ' and not ' + (2 * five + ten) + '.');
// "Fifteen is 15 and not 20."

const five = 5;
const ten = 10;
console.log(`Fifteen is ${five + ten} and not ${2 * five + ten}.`);
// "Fifteen is 15 and not 20."

国际化 Internationalization

Intl对象是ECMAScript Internationalization API

日期和时间格式化

const msPerDay = 24 * 60 * 60 * 1000;
 
// July 17, 2014 00:00:00 UTC.
const july172014 = new Date(msPerDay * (44 * 365 + 11 + 197));

const options = { year: '2-digit', month: '2-digit', day: '2-digit',
                hour: '2-digit', minute: '2-digit', timeZoneName: 'short' };
const americanDateTime = new Intl.DateTimeFormat('en-US', options).format;
 
console.log(americanDateTime(july172014)); // 07/16/14, 5:00 PM PDT

数值格式化

const gasPrice = new Intl.NumberFormat('en-US',
                        { style: 'currency', currency: 'USD',
                          minimumFractionDigits: 3 });
 
console.log(gasPrice.format(5.259)); // $5.259

const hanDecimalRMBInChina = new Intl.NumberFormat('zh-CN-u-nu-hanidec',
                        { style: 'currency', currency: 'CNY' });
 
console.log(hanDecimalRMBInChina.format(1314.25)); // ￥ 一,三一四.二五

校对

Collator对象用来比较和排序字符串

const names = ['Hochberg', 'Hönigswald', 'Holzman'];
 
const germanPhonebook = new Intl.Collator('de-DE-u-co-phonebk');
 
// as if sorting ["Hochberg", "Hoenigswald", "Holzman"]:
console.log(names.sort(germanPhonebook.compare).join(', '));
// logs "Hochberg, Hönigswald, Holzman"

const germanDictionary = new Intl.Collator('de-DE-u-co-dict');
 
// as if sorting ["Hochberg", "Honigswald", "Holzman"]:
console.log(names.sort(germanDictionary.compare).join(', '));
// logs "Hochberg, Holzman, Hönigswald"