Bad:
Array.prototype.diff = function diff(comparisonArray) {
const hash = new Set(comparisonArray);
return this.filter(elem => !hash.has(elem));
};
Good:
class SuperArray extends Array {
diff(comparisonArray) {
const hash = new Set(comparisonArray);
return this.filter(elem => !hash.has(elem));
}
}
比起命令式我更喜欢函数式编程
函数式变编程可以让代码的逻辑更清晰更优雅，方便测试。
Bad:
const programmerOutput = [
{
name: 'Uncle Bobby',
linesOfCode: 500
}, {
name: 'Suzie Q',
linesOfCode: 1500
}, {
name: 'Jimmy Gosling',
linesOfCode: 150
}, {
name: 'Gracie Hopper',
linesOfCode: 1000
}
];
let totalOutput = 0;
for (let i = 0; i < programmerOutput.length; i++) {
totalOutput += programmerOutput[i].linesOfCode;
}
Good:
const programmerOutput = [
{
name: 'Uncle Bobby',
linesOfCode: 500
}, {
name: 'Suzie Q',
linesOfCode: 1500
}, {
name: 'Jimmy Gosling',
linesOfCode: 150
}, {
name: 'Gracie Hopper',
linesOfCode: 1000
}
];
let totalOutput = programmerOutput
.map(output => output.linesOfCode)
.reduce((totalLines, lines) => totalLines + lines, 0)
封装条件语句
Bad:
if (fsm.state === 'fetching' && isEmpty(listNode)) {
// ...
}
Good:
function shouldShowSpinner(fsm, listNode) {
return fsm.state === 'fetching' && isEmpty(listNode);
}
if (shouldShowSpinner(fsmInstance, listNodeInstance)) {
// ...
}
尽量别用“非”条件句
Bad:
function isDOMNodeNotPresent(node) {
// ...
}
if (!isDOMNodeNotPresent(node)) {
// ...
}
Good:
function isDOMNodePresent(node) {
// ...
}
if (isDOMNodePresent(node)) {
// ...
}
避免使用条件语句
Q：不用条件语句写代码是不可能的。
A：绝大多数场景可以用多态替代。
Q：用多态可行，但为什么就不能用条件语句了呢？
A：为了让代码更简洁易读，如果你的函数中出现了条件判断，那么说明你的函数不止干了一件事情，违反了函数单一原则。
Bad:
class Airplane {
// ...
// 获取巡航高度
getCruisingAltitude() {
switch (this.type) {
case '777':
return this.getMaxAltitude() - this.getPassengerCount();
case 'Air Force One':
return this.getMaxAltitude();
case 'Cessna':
return this.getMaxAltitude() - this.getFuelExpenditure();
}
}
}
Good: