Pascal's triangle: Difference between revisions

=={{header|JavaScript}}==

{{works with|SpiderMonkey}}

{{works with|V8}}

<lang javascript>// Pascal's triangle object

function pascalTriangle (rows) {

// Number of rows the triangle contains

this.rows = rows;

// The 2D array holding the rows of the triangle

this.triangle = new Array();

for (var r = 0; r < rows; r++) {

this.triangle[r] = new Array();

for (var i = 0; i <= r; i++) {

if (i == 0 || i == r)

this.triangle[r][i] = 1;

else

this.triangle[r][i] = this.triangle[r-1][i-1]+this.triangle[r-1][i];

}

}

// Method to print the triangle formatted into a triangle

this.print = function(base) {

if (!base)

base = 10;

// Private method to calculate digits in number

var digits = function(n,b) {

var d = 0;

while (n >= 1) {

d++;

n /= b;

}

return d;

}

// Calculate max spaces needed

var spacing = digits(this.triangle[this.rows-1][Math.round(this.rows/2)],base);

// Private method to add spacing between numbers

var insertSpaces = function(s) {

var buf = "";

while (s > 0) {

s--;

buf += " ";

}

return buf;

}

for (var r = 0; r < this.triangle.length; r++) {

var l = "";

for (var s = 0; s < Math.round(this.rows-1-r); s++) {

l += insertSpaces(spacing);

}

for (var i = 0; i < this.triangle[r].length; i++) {

if (i != 0)

l += insertSpaces(spacing-Math.ceil(digits(this.triangle[r][i],base)/2));

l += this.triangle[r][i].toString(base);

if (i < this.triangle[r].length-1)

l += insertSpaces(spacing-Math.floor(digits(this.triangle[r][i],base)/2));

}

print(l);

}

}

}

// Display 4 row triangle in base 10

var tri = new pascalTriangle(4);

tri.print();

// Display 8 row triangle in base 16

tri = new pascalTriangle(8);

tri.print(16);</lang>

Output:

<pre>$ d8 pascal.js

1

1 1

1 2 1

1 3 3 1

1

1 1

1 2 1

1 3 3 1

1 4 6 4 1

1 5 a a 5 1

1 6 f 14 f 6 1

1 7 15 23 23 15 7 1

</pre>