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JavaScript WeakSet
tryjs_weakset_visitors
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<!DOCTYPE html> <html> <body> <h1>JavaScript WeakSet</h1> <p id="demo"></p> <script> let text = ""; // Create a WeakSet to track persons const persons = new WeakSet(); // Create Visitor Objects const John = {name:"John", age:40}; const Paul = {name:"Paul", age:41}; const Ringo = {name:"Ringo", age:42}; const George = {name:"George", age:43}; // Track visits track(Paul); track(Ringo); track(Paul); // Function to track visitors function track(visitor) { if (persons.has(visitor)) { text += visitor.name + " is visiting again.<br>"; } else { persons.add(visitor); text += visitor.name + ", age" + visitor.age +", is visiting for the first time<br>"; } } document.getElementById("demo").innerHTML = text; </script> </body> </html>