JS Built-ins

js-builtins.md

Built–Ins

alert() Sends message to user in small pop-up window

confirm() Asks for consent to move forward. Cancel returns false, OK returns true

prompt() Sends a message and retrieves an entry.

typeof() Useful for checking a variable's contents

• typeof true --> "boolean"
• typeof "derp" --> "string"
• typeof 42 --> "number"
• typeof undefined --> "undefined"
• typeof null --> "object"

var iceCream = prompt("What's your favorite ice cream flavor?");

typeof iceCream // Returns "object" if prompt() is set to null, ie, cancelled. 
                // Otherwise returns"string".