JavaScript While循环：变量不会替换为

Question

I have the following code:

j = 1;
while (j < 50) {
  //requirement:
     console.log(JSONitem [j]["criteria"]);
     reqtest = Object.keys(JSONitem [j]["criteria"]);
         ....
     j++;
}

But when I execute this, I get the following error:

TypeError: JSONitem[j] is undefined

The output object from the console.log part is right, but also in this line is the TypeErro above. I think, the "j" does not replace the number, but in the output console it works...

Thanks!

Answer 1

console.log(...JSONitem.map(el=>el.criteria));

Your code may behaves unexpected if the length of your array (?) changes. You should use the Array.prototype methods or the for..in, for..of or

for(i=0;i<array.length;i++) 

loops to iterate over your Array.