Printing Triangle star(*) pattern in javascript using Recursion [duplicate]

Question

I have been trying to solve printing down left side star(*) pattern in Javascript using recursion, i think my logic is correct but my syntax and concept might be wrong

// * * * * *
// * * * *
// * * *
// * *
// *

This is my code solution so far

var triangle = function (row, col) {
    if(row == 0){
        return
    }
    if(col < row){
        console.log("*")
        triangle(row, col + 1)
    }else{
        console.log("\n")
        triangle(row - 1, 0)
    }
}
triangle(4, 0)

output

*
*
*
*


*
*
*


*
*


*

But i want the output to be

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

Evidently, it is not possible to call console.log() without a newline. "You'll have to keep a string and concatenate if you want it all in one line..." — showdev
– showdev, Commented Nov 25, 2022 at 5:05

Hao Wu · Accepted Answer · 2022-11-25 05:11:16Z

1

console.log() closes the output stream automatically, the "line break" is because it is the next output session. You will see its true form if you use document.write.

var triangle = function (row, col) {
    if(row == 0){
        return
    }
    if(col < row){
        document.write("*")
        triangle(row, col + 1)
    }else{
        document.write("<br/>")
        triangle(row - 1, 0)
    }
}
triangle(4, 0)

But if you insist to use console.log(), some modification must be made:

var triangle = function (row, col, stream = '') {
    if(row == 0){
        return
    }
    if(col < row){
        stream += '*'
        triangle(row, col + 1, stream)
    }else{
        console.log(stream)
        stream = ''
        triangle(row - 1, 0, stream)
    }
}
triangle(4, 0)

edited Nov 25, 2022 at 5:11

answered Nov 25, 2022 at 5:06

Hao Wu

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1 Comment

Danities Ichaba Over a year ago

Thanks man..... I think I would go with the second solution, the first solution return an error when run in VS code "ReferenceError: document is not defined" since i am not running it on HTML environment

Maulik · Accepted Answer · 2022-11-25 05:08:05Z

0

check this solution

 function triangle(row){
        var print="";
        if(row==0){
            return;
        }
        for(var i=0;i<row;i++){
            print+="* "
        }
        console.log(print);
        triangle(row-1);
        
    }
    triangle(5);

answered Nov 25, 2022 at 5:08

Maulik

392 bronze badges

1 Comment

Danities Ichaba Over a year ago

Thanks man....I appreciate, this is cleaner but i think running it on for loop would increase it complexity(i might be wrong though)

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