每个 JavaScript 开发人员都应该知道的 7 个速记优化技巧

// Long-hand
const isVowel = (letter) => {
  if (
    letter === "a" ||
    letter === "e" ||
    letter === "i" ||
    letter === "o" ||
    letter === "u"
  ) {
    return true;
  }
  return false;
};
 
// Short-hand
const isVowel = (letter) =>
  ["a", "e", "i", "o", "u"].includes(letter);

const arr = [1, 2, 3, 4, 5];
 
// Long-hand
for (let i = 0; i < arr.length; i++) {
  const element = arr[i];
  // ...
}
 
// Short-hand
for (const element of arr) {
  // ...
}

const obj = {
  a: 1,
  b: 2,
  c: 3,
};
 
// Long-hand
const keys = Object.keys(obj);
for (let i = 0; i < keys.length; i++) {
  const key = keys[i];
  const value = obj[key];
  // ...
}
 
// Short-hand
for (const key in obj) {
  const value = obj[key];
  // ...
}

// Long-hand
const isFalsey = (value) => {
  if (
    value === null ||
    value === undefined ||
    value === 0 ||
    value === false ||
    value === NaN ||
    value === ""
  ) {
    return true;
  }
  return false;
};
 
// Short-hand
const isFalsey = (value) => !value;

// Long-hand
let info;
if (value < minValue) {
  info = "Value is too small";
} else if (value > maxValue) {
  info = "Value is too large";
} else {
  info = "Value is in range";
}
 
// Short-hand
const info =
  value < minValue
    ? "Value is too small"
    : value > maxValue ? "Value is too large" : "Value is in range";

function f1() {
  // ...
}
function f2() {
  // ...
}
 
// Long-hand
if (condition) {
  f1();
} else {
  f2();
}
 
// Short-hand
(condition ? f1 : f2)();

const dayNumber = new Date().getDay();
 
// Long-hand
let day;
switch (dayNumber) {
  case 0:
    day = "Sunday";
    break;
  case 1:
    day = "Monday";
    break;
  case 2:
    day = "Tuesday";
    break;
  case 3:
    day = "Wednesday";
    break;
  case 4:
    day = "Thursday";
    break;
  case 5:
    day = "Friday";
    break;
  case 6:
    day = "Saturday";
}
 
// Short-hand
const days = {
  0: "Sunday",
  1: "Monday",
  2: "Tuesday",
  3: "Wednesday",
  4: "Thursday",
  5: "Friday",
  6: "Saturday",
};
const day = days[dayNumber];

// Long-hand
let name;
if (user?.name) {
  name = user.name;
} else {
  name = "Anonymous";
}
 
// Short-hand
const name = user?.name || "Anonymous";