字符串 array generator

 

 

let b='designate'
console.log(b.charAt(2))
console.log(b[2])
console.log(b.toUpperCase())
console.log(b.concat('.com'))
console.log(b.slice(3))
console.log(b.slice(3,5))
console.log(b.slice(-2,-1))

let url='bbs.ibm.io'
console.log(url.split('.'))
console.log(url.substr(4,3))
console.log(url.substring(4,7))

let v='ibm.nebmt'
console.log(v.indexOf('bm'))
console.log((v.indexOf('bm',4)))
console.log(v.replace('.ne','.org'))

c=' \tnm io \r \n'
console.log(c.trim())

var biggestNum=Number.MAX_VALUE
var smallestNum=Number.MIN_VALUE
var infiniteNum=Number.POSITIVE_INFINITY
var negInfiniteNum=Number.NEGATIVE_INFINITY
var notANum=Number.NaN

console.log(biggestNum)
console.log(smallestNum)
console.log(infiniteNum)
console.log(negInfiniteNum)
console.log(notANum)

 

console.log(1/0)

console.log(parseInt('0.5'))

console.log(parseInt('faf'))
console.log('88'+8)

console.log(parseFloat('0.55'))
console.log(Math.abs(-2))
console.log(Math.PI)
console.log(Math.pow(2,3))
console.log(Math.sqrt(8))
console.log(1/2)
console.log(8%3)

let i=0;
let a=i++;
console.log(a,i)
console.log(a,i++)
a=++i;
console.log(a,i)

i=0;
a=++i+i+++i+++i;
console.log(a)

console.log('30a'>20)
console.log('30a'==30)
console.log(parseInt('30a5'))

console.log(300>'2000')
console.log('300'>'2000')

console.log(300>NaN)
console.log(300<NaN)
console.log(300==NaN)
console.log('#')
console.log(300=='300')
console.log(300==='300')
console.log('#')
console.log(3>Number.POSITIVE_INFINITY)
console.log(3<Number.NEGATIVE_INFINITY)

 

console.log('ui' instanceof String)
b=new String('ui')
console.log(b,b instanceof String,typeof(b),typeof(typeof(b)))
console.log(typeof(100),typeof(typeof(100)))
console.log(typeof('ui')==='string'?88:99)
console.log(22 instanceof Number)

 

x=44;
var y=88;
let z=99;
obj=new Number()
console.log(obj.h)
obj.h=2
obj.m='mm'
console.log(delete x)
console.log(delete y)
console.log(delete z)
console.log(delete obj.h)
console.log(delete obj)
console.log(delete Math.PI)

var trees=new Array('redwood','bay','cedar','oak','maple')

for(var i=0;i<trees.length;i++)
{
    console.log(trees[i])
}

delete trees[3]
for(var i=0;i<trees.length;++i)
{
    console.log(trees[i])
}

 

let trees = new Array('redwood', 'bay', 'cedar', 'oak', 'maple')
console.log(0 in trees)
console.log(3 in trees)
console.log(6 in trees)
console.log('bay' in trees)
console.log('length' in trees)

delete trees[3]

console.log(3 in trees)
for (var i = 0; i < trees.length; i++)
    console.log(trees[i])

let car = {
    brand: 'Honda',
    model: 'Accord',
    year: 1998
}
console.log('brand' in car)
console.log('model' in car)

 

生成器

function* b()
{
    let i=0;
    let j=5;
    for(;;){
        yield ++i;
        if(!j--) return 888;
        console.log(j)
    }
}

let v=b()

for(let i=0;i<10;i++){
    console.log(v.next())
}