1. The keyword switch can be followed by an expression or value in parentheses, usually a variable
  2. The keyword case, followed by the expression or value of an option, followed by a colon
  3. The value of the switch expression is compared to the value of the case in the structure
  4. If there is a matching congruence (===), the code block associated with the case is executed and stops when a break is encountered, terminating the entire switch statement code execution
  5. If all case values do not match the expression values, execute the code in default

The value in case is a judgment, which matches true in switch

<script>
        let score = prompt('Input score')
        score = parseFloat(score)

        switch (true) {
            case score >= 90:
                alert('A');
                break;
            case score >= 80:
                alert('B');
                break;
            default:
                alert('C');
        }
    </script>
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Case is a value that matches the variable in the switch

<script>
        // The prompt input box will pop up, asking the user to enter the fruit name, take the value and save it in the variable.
        // use this variable as the expression inside the switch parentheses.
        // use several different fruit names after case. Be sure to enclose them in quotes, as they must be congruent matches.
        // Pop up different prices. Also note that a break is added after each case to exit the switch statement.
        // Set default to no such fruit.
        var fruit = prompt('Please enter the fruit of enquiry :');
        switch (fruit) {
            case 'apple':
                alert('The price of apples is 3.5 per catty');
                break;
            case 'durian':
                alert('The price of durian is 35 per catty');
                break;
            default:
                alert('No such fruit');
        }
    </script>
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