Js learning, use of filter() function

let zq=["知青","知青学习"];
let newArray=zq.filter(function(value,index,arr){
    console.log(value,index,arr);
    return true;//返回值为true时，表示要这个值
});
console.log(newArray);

Case: filtering out js courses from all courses

let lesson=[{name:"学习js第一课",category:"js"},{name:"学习js第二课",category:"js"},{name:"学习python第一课",category:"python"}];
let res=lesson.filter(function(value){
    return value.category=="js";
});
console.table(res);