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1. If statements with multiple conditions

Place multiple values in an array and call the includes method of the array.

//longhand
if (x === 'abc' || x === 'def' || x === 'ghi' || x ==='jkl') {
    //logic
}
//shorthand
if (['abc', 'def', 'ghi', 'jkl'].includes(x)) {
   //logic
}
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If true… else

For if-else conditions that do not contain large logic, you can use the following shortcut. We can achieve this simplification simply by using the ternary operator.

//longhand
let test: boolean;
if (x > 100) {
    test = true;
} else {
    test = false;
}
// Shorthand
let test = (x > 10) ? true : false;
//or we can use directly
let test = x > 10;
console.log(test);
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You can do this if you have nested conditions.

let x = 300,
test2 = (x > 100) ? 'greater 100' : (x < 50) ? 'less 50' : 'between 50 and 100';
console.log(test2); // "greater than 100"
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Declare variables

We use this shorthand when we want to declare two variables that have the same value or the same type.

//Longhand 
let test1;
let test2 = 1;
//Shorthand 
let test1, test2 = 1;
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Check for null, undefined, and null values

When we create a new variable, we sometimes want to check that the referenced variable is not null or undefined. JavaScript does have a nice shortcut for this kind of checking.

// Longhand if (test1 ! == null || test1 ! == undefined || test1 ! == '') { let test2 = test1; } // Shorthand let test2 = test1 || '';Copy the code

Null checking and default assignment

let test1 = null,
    test2 = test1 || '';
console.log("null check", test2); // output will be ""
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Undefined check and default assignment

let test1 = undefined,
    test2 = test1 || '';
console.log("undefined check", test2); // output will be ""
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General value check

let test1 = 'test',
    test2 = test1 || '';
console.log(test2); // output: 'test'
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In addition, for points 4, 5 and 6 above, you can use?? Operators. If the left-hand value is null or undefined, the right-hand value is returned. By default, it returns the value on the left.

const test= null ?? 'default';
console.log(test);
// expected output: "default"
const test1 = 0 ?? 2;
console.log(test1);
// expected output: 0
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Assign values to multiple variables

This technique is useful when we want to assign values to multiple different variables.

//Longhand 
let test1, test2, test3;
test1 = 1;
test2 = 2;
test3 = 3;
//Shorthand 
let [test1, test2, test3] = [1, 2, 3];
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Handy assignment operator

In programming, we deal with a large number of arithmetic operators. This is one of the useful tricks for JavaScript variable assignment operators.

// Longhand
test1 = test1 + 1;
test2 = test2 - 1;
test3 = test3 * 20;
// Shorthand
test1++;
test2--;
test3 *= 20;
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9, if check whether the value exists

This is a common, easy technique that we all use, and it’s still worth mentioning here.

// Longhand if (test1 === true) or if (test1 ! == "") or if (test1 ! == null) // Shorthand //it will check empty string,null and undefined too if (test1)Copy the code

Note: If test1 has a value, the logic after if is performed. This operator is mainly used for null or undefinded checks.

The && operator for multiple criteria

If the function is called only when the variable is true, use the && operator.

//Longhand 
if (test1) {
 callMethod(); 
} 
//Shorthand 
test1 && callMethod();
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11. Foreach loop

This is a common loop simplification technique.

// Longhand
for (var i = 0; i < testData.length; i++)
// Shorthand
for (let i in testData) or  for (let i of testData)
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Iterate over each variable in the array.

function testData(element, index, array) {
  console.log('test[' + index + '] = ' + element);
}
[11, 24, 32].forEach(testData);
// logs: test[0] = 11, test[1] = 24, test[2] = 32
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12. Return after comparison

We can also use comparisons in return statements, which reduce five lines of code to one.

// Longhand let test; function checkReturn() { if (! (test === undefined)) { return test; } else { return callMe('test'); } } var data = checkReturn(); console.log(data); //output test function callMe(val) { console.log(val); } // Shorthand function checkReturn() { return test || callMe('test'); }Copy the code

Arrow function

//Longhand 
function add(a, b) { 
   return a + b; 
} 
//Shorthand 
const add = (a, b) => a + b;
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More examples:

function callMe(name) {
  console.log('Hello', name);
}
callMe = name => console.log('Hello', name);
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14. Short function calls

We can use the ternary operator to implement multiple function calls.

// Longhand
function test1() {
  console.log('test1');
};
function test2() {
  console.log('test2');
};
var test3 = 1;
if (test3 == 1) {
  test1();
} else {
  test2();
}
// Shorthand
(test3 === 1? test1:test2)();
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15. Switch simplification

We can store conditions in key-value objects and invoke them based on conditions.

// Longhand
switch (data) {
  case 1:
    test1();
  break;
  case 2:
    test2();
  break;
  case 3:
    test();
  break;
  // And so on...
}
// Shorthand
var data = {
  1: test1,
  2: test2,
  3: test
};
data[something] && data[something]();
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16, implicit return

By using the arrow function, we can return the value directly without a return statement.

//longhand
function calculate(diameter) {
  return Math.PI * diameter
}
//shorthand
calculate = diameter => (
  Math.PI * diameter;
)
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17. Exponential representation

// Longhand for (var i = 0; i < 10000; i++) { ... } // Shorthand for (var i = 0; i < 1e4; i++) {... }Copy the code

18. Default parameter values

//Longhand
function add(test1, test2) {
  if (test1 === undefined)
    test1 = 1;
  if (test2 === undefined)
    test2 = 2;
  return test1 + test2;
}
//shorthand
add = (test1 = 1, test2 = 2) => (test1 + test2);
add() //output: 3
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19. Extension operator simplification

// joining arrays using concat const data = [1, 2, 3]; const test = [4 ,5 , 6].concat(data); //shorthand // joining arrays const data = [1, 2, 3]; const test = [4 ,5 , 6, ...data]; console.log(test); // [4, 5, 6, 1, 2, 3]Copy the code

We can also clone using the extended operator.

//longhand
// cloning arrays
const test1 = [1, 2, 3];
const test2 = test1.slice()
//shorthand
// cloning arrays
const test1 = [1, 2, 3];
const test2 = [...test1];
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20. Template literals

If you’re tired of using + to concatenate multiple variables into a single string, this simplification trick will be a headache free.

//longhand
const welcome = 'Hi ' + test1 + ' ' + test2 + '.'
//shorthand
const welcome = `Hi ${test1} ${test2}`;
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21. Cross-line string

We can do this when dealing with cross-line strings in our code.

//longhand
const data = 'abc abc abc abc abc abc\n\t'
    + 'test test,test test test test\n\t'
//shorthand
const data = `abc abc abc abc abc abc
         test test,test test test test`
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22. Object attribute assignment

let test1 = 'a'; 
let test2 = 'b';
//Longhand 
let obj = {test1: test1, test2: test2}; 
//Shorthand 
let obj = {test1, test2};
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23. Convert strings to numbers

//Longhand let test1 = parseInt('123'); Let test2 = parseFloat (' 12.3 '); //Shorthand let test1 = +'123'; Let test2 = + '12.3';Copy the code

24. Deconstruct assignment

//longhand
const test1 = this.data.test1;
const test2 = this.data.test2;
const test2 = this.data.test3;
//shorthand
const { test1, test2, test3 } = this.data;
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25, array find simplification

The find method is useful when we have an array of objects and want to find specific objects based on their properties.

const data = [{
        type: 'test1',
        name: 'abc'
    },
    {
        type: 'test2',
        name: 'cde'
    },
    {
        type: 'test1',
        name: 'fgh'
    },
]
function findtest1(name) {
    for (let i = 0; i < data.length; ++i) {
        if (data[i].type === 'test1' && data[i].name === name) {
            return data[i];
        }
    }
}
//Shorthand
filteredData = data.find(data => data.type === 'test1' && data.name === 'fgh');
console.log(filteredData); // { type: 'test1', name: 'fgh' }
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Condition search simplification

If we want to call different methods based on different types, we can use multiple else if statements or switches, but is there a better simplification technique?

// Longhand if (type === 'test1') { test1(); } else if (type === 'test2') { test2(); } else if (type === 'test3') { test3(); } else if (type === 'test4') { test4(); } else { throw new Error('Invalid value ' + type); } // Shorthand var types = { test1: test1, test2: test2, test3: test3, test4: test4 }; var func = types[type]; (! func) && throw new Error('Invalid value ' + type); func();Copy the code

27. Simplified bitwise operation of indexOf

When looking for a value in an array, we can use the indexOf() method. But there’s a better way. Let’s look at this example.

//longhand if(arr.indexOf(item) > -1) { // item found } if(arr.indexOf(item) === -1) { // item not found } //shorthand if(~arr.indexOf(item)) { // item found } if(! ~arr.indexOf(item)) { // item not found }Copy the code

The bitwise () operator returns true (except -1), and the reverse operation only needs to be done! . Alternatively, you can use the include() function.

if (arr.includes(item)) { 
// true if the item found
}
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28, Object. Entries ()

This method converts an object to an array of objects.

const data = { test1: 'abc', test2: 'cde', test3: 'efg' };
const arr = Object.entries(data);
console.log(arr);
/** Output:
[ [ 'test1', 'abc' ],
  [ 'test2', 'cde' ],
  [ 'test3', 'efg' ]
]
**/
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29, the Object. The values ()

This is also a new feature introduced in ES8 and functions like Object.entries(), but without the keys.

const data = { test1: 'abc', test2: 'cde' };
const arr = Object.values(data);
console.log(arr);
/** Output:
[ 'abc', 'cde']
**/
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30. Double bitwise operation

// Longhand Math.floor(1.9) === 1 // true // Sleep ~~1.9 === 1 // trueCopy the code

31. Repeat string multiple times

We can use a for loop to repeatedly manipulate the same character, but there is an easier way.

//longhand 
let test = ''; 
for(let i = 0; i < 5; i ++) { 
  test += 'test '; 
} 
console.log(str); // test test test test test 
//shorthand 
'test '.repeat(5);
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Find the maximum and minimum value of the array

const arr = [1, 2, 3]; Math. Max (... arr); / / 3 Math. Min (... arr); / / 1Copy the code

Get the character of the string

let str = 'abc';
//Longhand 
str.charAt(2); // c
//Shorthand 
str[2]; // c
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34. Exponential power simplification

/ / longhand math.h pow (2, 3); // 8 //shorthand 2**3 // 8Copy the code

If there is wrong or meaningful place welcome message!

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