Java-script-course/06-booleans.html at main · Dev-Soft-tech/Java-script-course · GitHub

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<!DOCTYPE html>
<html>
  <head>
    <title>Booleans</title>
  </head>
  <body>
    <script>
      // console.log(typeof 'true'); //string
      // console.log(typeof true);  //boolean
      // false
      // console.log(3 > 5); //true
      // console.log(3 < 5); //false
      // console.log(3 === '5.00'); //false
      // if (true) {
      //   console.log('hello');
      // } //true
      // if (false) {
      //   console.log('hello');
      // } //false
      // if (true) {
      //   console.log('hello');
      // } else {
      //   console.log('else');
      // }
      // const age = 15
      // if(age <= 16){
      //   console.log('you can drive');
      // } else {
      //   console.log('you can not drive');
      // } //true you can drive.
      // if(30 <= 16){
      //   console.log('you can drive');
      // } else if (15 >= 14) {
      //   console.log('almost there');
      // }else {
      //   console.log('you can not drive');
      // } //true you can not drive.
      //and logical operator
      console.log(true && false); //false
      console.log(true && true); //true
      console.log(false && false); //true
      console.log(false && true); //false
      console.log(0.2 >= 0 && 0.2 < 1 / 3);
      //if the two or, any of the
      // sides are true the result will be true
      console.log(true || false);
      //OR logical operater
      //NOT operator flips the value of the boolean
      //if the value is true it will be false and
      //if the value is false it will be true
      //console.log(!true); //false
      //console.log(!false); //true

      if (0) {
        console.log('truthy'); //false
      }
      const cartQuantity = 5; //truthy value.
      if (cartQuantity) {
        console.log('cart has product')
      }
      console.log(!1); //false
      console.log(!0); //true
      console.log(0); //0
      console.log(!-2); //false
      console.log(!4); //false
      if (cartQuantity > 0) {
        console.log('cart has products');
      }
      //falsy values
      // NAN: not a number : invalid calculation
      // undefined: invalid number or don't have a value
      // SHORT CUTS FOR THE IF STATEMENTS
      // Ternerary operator
      // 'trutty is the if statement'
      // 'false is the else statement'
      true ? 'trutty' : 'false';
      const result = true ? 'trutty' : 'false';
      // Gard operator !!
      //and operator stops the execution of the code if the first value is false
      true && console.log("hello"); //prints out the message hello
      const maessage = false && console.log("hello");
      console.log(maessage); //the value false will be saved inside the varaible
      // any number posible from 1 to infinity is a truthy
      // 0 is a falsy value
      const maes = true && console.log("hello");
      console.log(maes); //value will be undefined.
      //dafault operator
      const currency = 'EUR' || 'USD';
      console.log(currency); //EUR
      const currenc = undefined || 'USD';
      console.log(currenc); //uUSD
    </script>
  </body>
</html>