JavaScript if judgment, ternary operator, loop

if judgment

let score=162;

if(score>=80){
    
    
    alert("优秀");
}else if(score>=60){
    
    
    alert("及格");
}else{
    
    
    alert("不及格");
}

Ternary operator

let a=110;
let b=20;
let max_num = a>b ? a : b;
alert(max_num);

loop structure

while loop

let a=10;
while(a>=0){
    
    
    console.log(a);
    a-=2;
}

for loop

for(let i=1;i<5;i++){
    
    
    console.log(i);
}

for loop array

let arr=[2,9,7,2,7,2];
arr['a']="李白";
arr['b']="杜甫";

for(let i in arr){
    
    
    console.log(i,arr[i]);
}

Only parts of an indexed array can be traversed

let arr=[2,9,7,2,7,2];
arr['a']="李白";
arr['b']="杜甫";

arr.forEach(function(val,index){
    
    
    console.log(index,val);
});

loop string

let str="abcdbaba";  
for(let i=0;i<=str.length-1;i++){
    
    
    console.log(i,str[i]);
}