字符串的扩展

var str = "hello";
 
for(let i of str) {
    console.log(i);
}

var s = ‘Hello world!‘;
 
s.startsWith(‘Hello‘) // true
s.endsWith(‘!‘) // true
s.includes(‘o‘) // true

‘x‘.repeat(3) // "xxx"

‘x‘.padStart(5, ‘ab‘) // ‘ababx‘
‘x‘.padStart(4, ‘ab‘) // ‘abax‘
‘x‘.padEnd(5, ‘ab‘) // ‘xabab‘
‘x‘.padEnd(4, ‘ab‘) // ‘xaba‘

// 普通字符串
`In JavaScript ‘\n‘ is a line-feed.`
 
// 多行字符串
`In JavaScript this is
not legal.`
 
// 字符串中嵌入变量
var name = "Bob", time = "today";
`Hello ${name}, how are you ${time}?`

alert`123`
// 等同于
alert(123)