This article brings you technical writing methods (code examples) about complex logical judgments in JavaScript. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.
We often encounter complex logical judgments when writing js code. Usually you can use if/else or switch to implement multiple conditional judgments, but this will cause a problem. As the logic becomes more complex, As the speed increases, the if/else/switch in the code will become more and more bloated and difficult to understand. So how to write judgment logic more elegantly, this article will give you a try.
For example
Look at a piece of code first
/**
* 按钮点击事件
* @param {number} status 活动状态：1 开团进行中 2 开团失败 3 商品售罄 4 开团成功 5 系统取消
*/
const onButtonClick = (status) => {
if (status == 1) {
sendLog('processing') jumpTo('IndexPage')
} else if (status == 2) {
sendLog('fail') jumpTo('FailPage')
} else if (status == 3) {
sendLog('fail') jumpTo('FailPage')
} else if (status == 4) {
sendLog('success') jumpTo('SuccessPage')
} else if (status == 5) {
sendLog('cancel') jumpTo('CancelPage')
} else {
sendLog('other') jumpTo('Index')
}
}You can see the click logic of this button through the code: do two things according to different activity states Things, send the log to bury the point and jump to the corresponding page. You can easily propose a rewriting plan for this code. The switch appears:
/**
* 按钮点击事件
* @param {number} status 活动状态：1 开团进行中 2 开团失败 3 商品售罄 4 开团成功 5 系统取消
*/
const onButtonClick = (status) => {
switch (status) {
case 1:
sendLog('processing')
jumpTo('IndexPage')
break
case 2:
case 3:
sendLog('fail')
jumpTo('FailPage')
break
case 4:
sendLog('success')
jumpTo('SuccessPage')
break
case 5:
sendLog('cancel')
jumpTo('CancelPage')
break
default:
sendLog('other')
jumpTo('Index')
break
}
}Well, this looks much clearer than if/else, be careful. My classmates also discovered a little trick. When case 2 and case 3 have the same logic, you can omit the execution statement and break. Then the logic of case 3 will be automatically executed in case 2.
At this time, some students will say that there is a simpler way to write:
const actions = {
'1': ['processing', 'IndexPage'],
'2': ['fail', 'FailPage'],
'3': ['fail', 'FailPage'],
'4': ['success', 'SuccessPage'],
'5': ['cancel', 'CancelPage'],
'default': ['other', 'Index'],
}
/**
* 按钮点击事件
* @param {number} status 活动状态：1开团进行中 2开团失败 3 商品售罄 4 开团成功 5 系统取消
*/
const onButtonClick = (status) => {
let action = actions[status] || actions['default'],
logName = action[0],
pageName = action[1]
sendLog(logName)
jumpTo(pageName)
}The above code does look cleaner. The smart thing about this method is that it takes the judgment condition as an object The attribute name uses the processing logic as the attribute value of the object. When the button is clicked, logical judgment is made by searching the object attributes. This writing method is particularly suitable for unary conditional judgment.
Is there any other way to write it? Some:
const actions = new Map([
[1, ['processing', 'IndexPage']],
[2, ['fail', 'FailPage']],
[3, ['fail', 'FailPage']],
[4, ['success', 'SuccessPage']],
[5, ['cancel', 'CancelPage']],
['default', ['other', 'Index']]
])
/**
* 按钮点击事件
* @param {number} status 活动状态：1 开团进行中 2 开团失败 3 商品售罄 4 开团成功 5 系统取消
*/
const onButtonClick = (status) => {
let action = actions.get(status) || actions.get('default')
sendLog(action[0])
jumpTo(action[1])
}Writing like this uses the Map object in es6. Isn’t it more fun? What is the difference between Map object and Object object?
1. An object usually has its own prototype, so an object always has a "prototype" key.
2. The key of an object can only be a string or Symbols, but the key of a Map can be any value.
3. You can easily get the number of key-value pairs of a Map through the size attribute, while the number of key-value pairs of an object can only be confirmed manually.
We need to upgrade the problem. In the past, we only needed to judge the status when clicking the button. Now we also need to judge the user's identity:
/**
* 按钮点击事件
* @param {number} status 活动状态：1开团进行中 2开团失败 3 开团成功 4 商品售罄 5 有库存未开团
* @param {string} identity 身份标识：guest客态 master主态
*/
const onButtonClick = (status, identity) => {
if (identity == 'guest') {
if (status == 1) {
//do sth
} else if (status == 2) {
//do sth
} else if (status == 3) {
//do sth
} else if (status == 4) {
//do sth
} else if (status == 5) {
//do sth
} else {
//do sth
}
} else if (identity == 'master') {
if (status == 1) {
//do sth
} else if (status == 2) {
//do sth
} else if (status == 3) {
//do sth
} else if (status == 4) {
//do sth
} else if (status == 5) {
//do sth
} else {
//do sth
}
}
}Forgive me for not writing the specific logic of each judgment. Because the code is too verbose.
Forgive me for using if/else again, because I see many people still using if/else to write such large sections of logical judgment.
We can see from the above example that when your logic is upgraded to binary judgment, your judgment amount will double, and your code amount will also double. How to write more refreshingly at this time?
const actions = new Map([
['guest_1', () => { /*do sth*/ }],
['guest_2', () => { /*do sth*/ }],
['guest_3', () => { /*do sth*/ }],
['guest_4', () => { /*do sth*/ }],
['guest_5', () => { /*do sth*/ }],
['master_1', () => { /*do sth*/ }],
['master_2', () => { /*do sth*/ }],
['master_3', () => { /*do sth*/ }],
['master_4', () => { /*do sth*/ }],
['master_5', () => { /*do sth*/ }],
['default', () => { /*do sth*/ }],
])
/**
* 按钮点击事件
* @param {string} identity 身份标识：guest客态 master主态
* @param {number} status 活动状态：1 开团进行中 2 开团失败 3 开团成功 4 商品售罄 5 有库存未开团
*/
const onButtonClick = (identity, status) => {
let action = actions.get(`${identity}_${status}`) || actions.get('default')
action.call(this)
}The core logic of the above code is: splice the two conditions into a string, and search and execute the Map object using the conditional string as the key and the processing function as the value. This writing method is used in multiple It is especially useful when making conditional judgments.
Of course, if the above code is implemented using Object objects, it will be similar:
const actions = {
'guest_1': () => { /*do sth*/ },
'guest_2': () => { /*do sth*/ },
//....
}
const onButtonClick = (identity, status) => {
let action = actions[`${identity}_${status}`] || actions['default']
action.call(this)
}
如果有些同学觉得把查询条件拼成字符串有点别扭，那还有一种方案，就是用Map对象，以Object对象作为key：
const actions = new Map([
[{
identity: 'guest',
status: 1
}, () => { /*do sth*/ }],
[{
identity: 'guest',
status: 2
}, () => { /*do sth*/ }],
//...
])
const onButtonClick = (identity, status) => {
let action = [...actions].filter(([key, value]) => (key.identity == identity && key.status == status))
action.forEach(([key, value]) => value.call(this))
}Is it a little more advanced?
The difference between Map and Object can also be seen here. Map can use any type of data as key.
Now we will upgrade the difficulty a little bit. What if the processing logic of status1-4 is the same in the guest case. The worst case is this:
const actions = new Map([
[{
identity: 'guest',
status: 1
}, () => { /* functionA */ }],
[{
identity: 'guest',
status: 2
}, () => { /* functionA */ }],
[{
identity: 'guest',
status: 3
}, () => { /* functionA */ }],
[{
identity: 'guest',
status: 4
}, () => { /* functionA */ }],
[{
identity: 'guest',
status: 5
}, () => { /* functionB */ }],
//...
])A better way to write it is Cache the processing logic function:
const actions = () => {
const functionA = () => { /*do sth*/ }
const functionB = () => { /*do sth*/ }
return new Map([
[{
identity: 'guest',
status: 1
}, functionA],
[{
identity: 'guest',
status: 2
}, functionA],
[{
identity: 'guest',
status: 3
}, functionA],
[{
identity: 'guest',
status: 4
}, functionA],
[{
identity: 'guest',
status: 5
}, functionB],
//...
])
}
const onButtonClick = (identity, status) => {
let action = [...actions()].filter(([key, value]) => (key.identity == identity && key.status == status))
action.forEach(([key, value]) => value.call(this))
}Writing like this can already meet daily needs, but to be serious, it is still a bit uncomfortable to rewrite functionA 4 times above. If the judgment condition becomes particularly complicated, for example, identity has There are 3 states, and status has 10 states. Then you need to define 30 processing logics, and often many of these logics are the same. This seems to be something I don’t want to accept. It can be implemented like this:
const actions = () => {
const functionA = () => { /*do sth*/ }
const functionB = () => { /*do sth*/ }
return new Map([
[/^guest_[1-4]$/, functionA],
[/^guest_5$/, functionB],
//...
])
}
const onButtonClick = (identity, status) => {
let action = [...actions()].filter(([key, value]) => (key.test(`${identity}_${status}`)))
action.forEach(([key, value]) => value.call(this))
}The advantages of Map are more prominent here. Regular types can be used as keys, which opens up unlimited possibilities. If the demand changes, a log burying point must be sent for all guest situations, and different status situations also require separate logical processing, then we You can write it like this:
const actions = () => {
const functionA = () => { /*do sth*/ }
const functionB = () => { /*do sth*/ }
const functionC = () => { /*send log*/ }
return new Map([
[/^guest_[1-4]$/, functionA],
[/^guest_5$/, functionB],
[/^guest_.*$/, functionC],
//...
])
}
const onButtonClick = (identity, status) => {
let action = [...actions()].filter(([key, value]) => (key.test(`${identity}_${status}`)))
action.forEach(([key, value]) => value.call(this))
}That is to say, using the characteristics of array loops, logic that meets the regular conditions will be executed. Then you can execute public logic and individual logic at the same time. Because of the existence of regular rules, you can open up your imagination. To unlock more ways to play, I won’t go into details in this article.
This article has taught you 8 ways to write logical judgments, including:
if/else
switch
When judging by one element: Save it in Object
When judging by one element: Save it in Map
When making multiple judgments: Splice the condition into a string and save it in Object
When making multiple judgments: Splice the condition into a string and save it into In Map
When making multiple judgments: Save the condition as Object and save it in Map
When making multiple judgments: Save the condition as regular expression in Map里
At this point, this article will come to an end. I hope that your future life will not only have if/else/switch.
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