Node.js 图案

Question

var readline=require("readline-sync");
var n=parseInt(readline.question());

for (var i=1;i<=n;i++){
  var str="";
for (var j=1;j<=i;j++){
str+="*";
  console.log(str);

}console.log();

}

Plesse tell me where I am doing wrong. I want to print a pattern for

*
**
***
****
***** 

Also please tell me where I can do improvements. Thanks !

Answer 1

You need to know better about variable scopes. var is hoisted to the module level that why str is not defined on each iteration of your outer for loop. See Closure

Just use let instead of var to define str in a for block scope.

for (var i=1;i<=n;i++){
  let str="";
  for (var j=1;j<=i;j++){
    str+="*";
    console.log(str);
  }
  console.log();
}

Answer 2

You are printing that string every time you append a * to string. and you can fix it using following

 n=5 for (var i=0;i<n;i++){ var str=""; for (var j=0;j<=i;j++){ str+="*"; } console.log(str); }