Programming examples without If statements

From now on, please try to avoid using if statements to implement our business

You may wonder what are the benefits of not using if? Well~, maybe there is no obvious benefit, it is just to change the way of thinking to solve the problem. There is nothing wrong with if-else, but in some cases a large number of if-else may make the code less readable. Below are some examples to help you feel the mystery.

Coding Tip: Try to Code Without If-statements

##Challenge #1: Count how many odd numbers there are in the numerical array

We know an integer type array, count the number of odd numbers in the array

const arrayOfIntegers = [1, 4, 5, 9, 0, -1, 5];

if implementation

let counter = 0;
arrayOfIntegers.forEach((integer) => {
  const remainder = Math.abs(integer % 2);
  if (remainder === 1) {
    counter++;
  }
});
console.log(counter);

non-if implementation

let counter = 0;
arrayOfIntegers.forEach((integer) => {
  const remainder = Math.abs(integer % 2);
  // 偶数除2的余数为零，奇数的余数为一
  counter += remainder;
});
console.log(counter);

Note: The above two For example, forEach will change the original array, and the method is

variable, which violates the immutable concept of functional programming currently advocated. Don't worry, it is not the focus of this article. Comparing the two examples, the implementation of the if statement may be more compatible and can be adapted to the situation where the array element is a decimal. If the array elements are of floating point type, the second example will not work properly.

Challenge #2: Determine whether a date is a weekend or a working day

Implement a function, date object

new Date()as input, return the current day based on different datesWorkday or Weekend.

if implementation

const weekendOrWeekday = inputDate => {
  const day = inputDate.getDay();
  if (day === 0 || day === 6) {
    return 'weekend';
  }

  return 'weekday';
  // Or, for ternary fans:
  // return (day === 0 || day === 6) ? 'weekend' : 'weekday';
};
console.log(weekendOrWeekday(new Date()));

Non-if implementation

const weekendOrWeekday = (inputDate) => {
  const day = inputDate.getDay();
  return weekendOrWeekday.labels[day] ||
         weekendOrWeekday.labels['default'];
};
weekendOrWeekday.labels = {
  0: 'weekend',
  6: 'weekend',
  default: 'weekday'
};
console.log(weekendOrWeekday(new Date()));

Have you noticed that the number in

if statement represents which day is the weekend, and determines the conditional distribution The ones are relatively scattered. What we need to do is to correspond the numbers to the weekend or weekday types. For example, in Example 2, you can use an object or map to store the corresponding relationship.

Comparing the above two examples, it can be clearly seen that

non-if codeimplementation has better readability and scalability

Challenge #3: The doubler function ( here be dragons), can’t be translated~Awkward~

Implement a doubler function, and do the following processing according to different inputs:

1. If the input is

   number type, do double processing (5 => 10, -10 => -20)

2. If the input is

   string type, repeat each Characters ('hello' => 'hheelloo')

3. If the input is of type

   function, the function

will be called and executed twice
4. If the input is of type

   array, perform doubler processing on each element of the array

5. If the input is

   objectType, do doubler processing for each attribute of the object

##switch

implementation<pre class="brush:php;toolbar:false">const doubler = (input) =&gt; {   switch (typeof input) {     case 'number':       return input + input;     case 'string':       return input         .split('')         .map(letter =&gt; letter + letter)         .join('');     case 'object':       Object.keys(input)             .map(key =&gt; (input[key] = doubler(input[key])));       return input;     case 'function':       input();       input();   } }; console.log(doubler(-10)); console.log(doubler('hey')); console.log(doubler([5, 'hello'])); console.log(doubler({ a: 5, b: 'hello' })); console.log(   doubler(function() {     console.log('call-me');   }), );</pre>non

switch

Implementation<pre class="brush:php;toolbar:false">const doubler = (input) =&gt; {   return doubler.operationsByType[typeof input](input); }; doubler.operationsByType = {   number: (input) =&gt; input + input,   string: (input) =&gt;     input       .split('')       .map((letter) =&gt; letter + letter)       .join(''),   function: (input) =&gt; {     input();     input();   },   object: (input) =&gt; {     Object.keys(input)           .map((key) =&gt; (input[key] = doubler(input[key])));     return input;   }, }; console.log(doubler(-10)); console.log(doubler('hey')); console.log(doubler([5, 'hello'])); console.log(doubler({ a: 5, b: 'hello' })); console.log(   doubler(function() {     console.log('call-me');   }), );</pre> is similar to Challenge #2, aggregating condition values ​​together for unified processing.

Summary

When there are many judgment conditions for

if-else

, the conditions are processed centrally (use object to store their corresponding relationships - the condition is used as key, and the processing is used as value ). The advantage is that it becomes easier to add or delete a certain condition, and the code is more readable. It is recommended to use the key-value correspondence to replace part of the if-else conditional judgment. Related recommendations:

Talk about the current situation, prospects and opportunities of the if statement

The code of the elseif statement based on PHP Example summary

Detailed explanation of if statement in sql

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