示例1：具有if..else if … else的简单计算器
// program for a simple calculator
// take the operator input
let operator = prompt('Enter operator ( either +, -, * or / ): ');
// take the operand input
let number1 = parseFloat(prompt('Enter first number: '));
let number2 = parseFloat(prompt('Enter second number: '));
let result;
// using if...else if... else
if (operator == '+') {
result = number1 + number2;
}
else if (operator == '-') {
result = number1 - number2;
}
else if (operator == '*') {
result = number1 * number2;
}
else {
result = number1 / number2;
}
// display the result
console.log(`${number1} ${operator} ${number2} = ${result}`);输出
Enter operator ( either +, -, * or / ): *
Enter first number: 3.4
Enter second number: 5.6
3.4 * 5.6 = 19.04在上面的示例中，提示用户输入一个运算符 ( + ， – ， *或/)和两个数字。
parseFloat()将数字字符串值转换为浮点值。
if...else if...if语句用于检查用户为运算符输入的条件。执行相应的操作并显示输出。
示例2：带开关的简单计算器
// program for a simple calculator
let result;
// take the operator input
let operator = prompt('Enter operator ( either +, -, * or / ): ');
// take the operand input
let number1 = parseFloat(prompt('Enter first number: '));
let number2 = parseFloat(prompt('Enter second number: '));
switch(operator) {
case '+':
result = number1 + number2;
console.log(`${number1} + ${number2} = ${result}`);
break;
case '-':
result = number1 - number2;
console.log(`${number1} - ${number2} = ${result}`);
break;
case '*':
result = number1 * number2;
console.log(`${number1} * ${number2} = ${result}`);
break;
case '/':
result = number1 / number2;
console.log(`${number1} / ${number2} = ${result}`);
break;
default:
console.log('Invalid operator');
break;
}输出
Enter operator: +
Enter first number: 4
Enter second number: 5
4 + 5 = 9在上述程序中，要求用户输入+ ， – ， *或/以及两个数字。然后， switch语句根据用户输入执行案例。