convert cs122a midterm CDF to PMF

cdf2pmf.js

var cdf = [1, 1, 1, 1, 1, 1, 4, 5, 11, 21, 34, 56, 84, 126, 181, 226, 261, 294, 305, 311, 312];
var pdf = cdf.slice(0, 1).concat(cdf.map((e, i) => e - cdf[i - 1]).slice(1));
var max = pdf.reduce((a, b) => Math.max(a, b));
var log = "";
for (let r = 0; r <= max; r++) {
	for (let c = 0; c < pdf.length; c++) {
		var y = max - pdf[c];
		if (y < r) {
			log += "|++++|  ";
		}
		else {
			if (y - 1 < r) {
				var x = max - r;
				log += "    " + (x < 10 ? " " : "") + x + "  ";
			}
			else {
				log += "        ";
			}
		}
	}
	log += "\n";
}
for (let c = 0; c < pdf.length; c++) {
	log += "--------";
}
log += "\n";
for (let c = 0; c < pdf.length; c++) {
	d = c * 4 + 8
	log += d + (d < 10 ? " " : "") + "      ";
}
console.log(log);