es6数组扩展

{
  let arr = Array.of(3,4,7,9,11);
  console.log('arr=',arr);     // [3, 4, 7, 9, 11]
  let empty=Array.of();
  console.log('empty',empty); // []
}

{
  let p=document.querySelectorAll('p');
  let pArr=Array.from(p);
  pArr.forEach(function(item){
    console.log(item.textContent);  //输出所有p标签的内容
  });

  console.log(Array.from([1,3,5],function(item){return item*2}));
  //[2,6,10]
}

{
  console.log('fill-7',[1,'a',undefined].fill(7)); //[7,7,7]  
  console.log('fill,pos',['a','b','c'].fill(7,1,3)); //["a",7,7]  //起始1 结束3  包括起始不包括结束
}

{
  for(let index of ['1','c','ks'].keys()){
    console.log('keys',index);  // 0,1,2  keys()表示的是数组下标
  }
  for(let value of ['1','c','ks'].values()){
    console.log('values',value); //1,c,ks 取的是值
  }
  for(let [index,value] of ['1','c','ks'].entries()){
    console.log('values',index,value); //索引和值都取
  }
}

{
  console.log([1,2,3,4,5].copyWithin(0,3,4)); //[4,2,3,4,5]
  //起始是3 结束是4 包括起始不包括结束，所以取的是数值4 ，把取到的覆盖到0这个位置
}

{
  console.log([1,2,3,4,5,6].find(function(item){return item>3}));   //4
  console.log([1,2,3,4,5,6].findIndex(function(item){return item>3})); //3
}

{
  console.log('number',[1,2,NaN].includes(1));  //true
  console.log('number',[1,2,NaN].includes(NaN)); //true
}