every,some,filter 都需要return 返回值boolean

every

        var arr = [{name:"cheng",state:true},{name:"html",state:false}];
        /* every,some,filter 都需要return   返回值boolean*/
        var b = arr.every(item=>item.state)  // (item>=item.state==true)
        console.log(b)

some

        var arr = [1,2,3,4];
        var b = arr.some(item=>item>1);
        console.log(b);

filter

        var arr = [
        {city:"武汉",state:true,spell:"wuhan"},
        {city:"北京",state:false,spell:"beijing"},
        {city:"武昌",state:false,spell:"wuchang"}
        ]
        var keyword = "武";
        var res = arr.filter(item=>{
            //return item.city.includes(keyword);
            if(item.city.includes(keyword) || item.spell.includes(keyword)){
                return item;
            }
        })
        console.log(res);