Built-in required, pattern, min/max and checkValidity().

• Category: JS Form Validation — part of the JavaScript Tutorial on GoCareerGo
• Read the short summary above, then check the linked docs for full syntax/behaviour
• Interview tip: be ready to explain "HTML5 Constraint Validation API" in one sentence, then back it up with a tiny example

// HTML5 Constraint Validation API — minimal example
console.log("HTML5 Constraint Validation API");