Initial commit.

1 year ago · e1784d3a13
commit e1784d3a13
2 changed files with 103 additions and 0 deletions
--- a/index.html
+++ b/index.html
@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<html>
+  <head><title>doUntil example</title></head>
+  <body style="text-align:center">
+    <div id="display">Press one of the buttons below</div>
+    <p>
+      <button onclick="findPrimesBlocking()">Find Primes (Blocking)</button>
+      <button onclick="findPrimesNonBlocking()">Find Primes (Non-Blocking)</button>
+    </p>
+    <script src="script.js"></script>
+  </body>
+</html>
--- a/script.js
+++ b/script.js
@ -0,0 +1,91 @@
+function doUntil(loop, stopCondition, yieldCondition) {
+
+    // Wrap function in promise so it can run asynchronously
+    return new Promise((resolve, reject) => {
+
+	// Build outerLoop function to pass to setTimeout
+	let outerLoop = function () {
+	    while (true) {
+		
+		// Execute a single loop
+		loop();
+
+		if (stopCondition()) {
+		    // Resolve promise, exit outer loop, and do not re-enter
+		    resolve();
+		    break;
+		} else if (yieldCondition()) {
+		    // Exit loop and queue up more iterations
+		    // for next event cycle
+		    setTimeout(outerLoop, 0);
+		    break;
+		}
+		
+		// Continue to next loop without yielding
+	    }
+	};
+
+	// Start the first iteration, unless the stop condition is met 
+	if (!stopCondition()) {
+	    setTimeout(outerLoop, 0);
+	}
+    });
+}
+
+// Check whether n is prime, given a list of all primes < n
+function isPrime(n, primes) {
+    for (const p of primes) {
+	if (n % p == 0) {
+	    return false;
+	}
+    }
+    return true;
+}
+
+function findPrimesBlocking() {
+    let primes = [];
+
+    for (let n = 2; n < 1000000; n++) {
+	if (isPrime(n, primes)) {
+	    primes.push(n);
+	}
+	if (n % 10000 == 0) {
+	    document.getElementById("display").textContent =
+		`Found ${primes.length} primes between 2 and ${n}`;
+	}
+    }
+    document.getElementById("display").textContent =
+	`Found ${primes.length} primes between 2 and 1000000`;
+}
+
+function findPrimesNonBlocking() {
+
+    // Initialize loop variable and list of primes
+    let n = 2;
+    let primes = [];
+
+    // Yield every 1000 iterations and stop after 1000000
+    const stopCondition = () => n == 1000000;
+    const yieldCondition = () => n % 10000 == 0;
+
+    // Build the loop body to be passed to doUntil()
+    const loop = () => {
+
+	// Determine if n is prime
+	if (isPrime(n, primes)) {
+	    primes.push(n);
+	}
+
+	// Increment n
+	n += 1;
+
+	// Update DOM if we're about to yield
+	if (yieldCondition()) {
+	    document.getElementById("display").textContent =
+		`Found ${primes.length} primes between 2 and ${n}`;
+	}
+    };
+
+    // Execute
+    doUntil(loop, stopCondition, yieldCondition);
+}