JavaScript 中的条件语句和循环

if (condition) {
  // code to execute if condition is true
} else {
  // code to execute if condition is false
}

let age = 18;
if (age >= 18) {
  console.log("you are eligible to vote.");
} else {
  console.log("you are not eligible to vote.");
}

let score = 75;
if (score >= 90) {
  console.log("grade: a");
} else if (score >= 75) {
  console.log("grade: b");
} else {
  console.log("grade: c");
}

switch (expression) {
  case value1:
    // code to execute if expression === value1
    break;
  case value2:
    // code to execute if expression === value2
    break;
  default:
    // code to execute if no cases match
}

let day = 3;
switch (day) {
  case 1:
    console.log("monday");
    break;
  case 2:
    console.log("tuesday");
    break;
  case 3:
    console.log("wednesday");
    break;
  default:
    console.log("invalid day");
}

for (initialization; condition; increment/decrement) {
  // code to execute
}

for (let i = 1; i <= 5; i++) {
  console.log("count:", i);
}

while (condition) {
  // code to execute
}

let count = 1;
while (count <= 5) {
  console.log("count:", count);
  count++;
}

do {
  // code to execute
} while (condition);

let count = 1;
do {
  console.log("count:", count);
  count++;
} while (count <= 5);

for (let i = 1; i <= 10; i++) {
  if (i === 5) break; // stops the loop when i is 5
  console.log(i);
}

for (let i = 1; i <= 10; i++) {
  if (i === 5) continue; // skips iteration when i is 5
  console.log(i);
}

let password = "abc123";
if (password.length >= 8) {
  console.log("password is valid.");
} else {
  console.log("password must be at least 8 characters long.");
}

let start = 1;
let end = 10;
console.log("Counting from 1 to 10:");
for (let i = start; i <= end; i++) {
  console.log(i);
}