Another 4 JavaScript tips for shorter code

Photo by Lukas Blazek on Unsplash

This is a continuation to my earlier article : 4 JavaScript tips for shorter code

1. Replace Switch and If-Else with key value pairs

The switch statement and if-else statement evaluates an expression and executes expressions conditionally. But as the number of cases increases the code grows as well.

//using switch
function returnDaySwitch(val) {
  switch (val) {
    case 1:
      return "It's monday"
    case 2:
      return "It's tuesday"
    case 3:
      return "It's wednesday"
    case 4:
      return "It's thursday"
    case 5:
      return "It's friday"
    case 6:
      return "It's saturday"
    case 7:
      return "It's sunday"
    default:
      return 'Enter a value between 1 - 7'
  }
}
//using if-else
function returnDayIfElse(val) {
  if (val == 1) {
    return "It's monday"
  } else if (val == 2) {
    return "It's tuesday"
  } else if (val == 3) {
    return "It's wednesday"
  } else if (val == 4) {
    return "It's thursday"
  } else if (val == 5) {
    return "It's friday"
  } else if (val == 6) {
    return "It's saturday"
  } else if (val == 7) {
    return "It's sunday"
  } else {
    return 'Enter a value between 1 - 7'
  }
}
const day = 3
console.log(returnDaySwitch(day)) //It's wednesday
console.log(returnDayIfElse(day)) //It's wednesday

This can be made simpler by using key-value pairs of an object.

function returnDayKeyValue(val) {
    const returnDayObject = {
        1: "It's monday",
        2: "It's tuesday",
        3: "It's wednesday",
        4: "It's thursday",
        5: "It's friday",
        6: "It's saturday",
        7: "It's sunday",
    }
    if(!returnDayObject[val]){
     return "Enter a value between 1 - 7";
    }
    return returnDayObject[val]
}
cosnt day = 3;
console.log(returnDayKeyValue(day)); //It's wednesday

Julian BRUXELLE Shared a way to get away with the if-else inside the function

const returnDayKeyValue = (val) => {
  const returnDayObject = {
    1: "It's monday",
    2: "It's tuesday",
    3: "It's wednesday",
    4: "It's thursday",
    5: "It's friday",
    6: "It's saturday",
    7: "It's sunday",
  }
  returnDayObject[val] ?? "Enter a value between 1 - 7";
}

This can be even made shorter.

const dayToString = day =>
    ({
        1: "It's Monday",
        2: "It's Tuesday",
        3: "It's Wednesday",
        4: "It's Thursday",
        5: "It's Friday",
        6: "It's Saturday",
        7: "It's Sunday",
    }[day] ?? "Enter a value between 1 - 7");

Or

const dayToString = day =>
    [
        undefined,
        "It's Monday",
        "It's Tuesday",
        "It's Wednesday",
        "It's Thursday",
        "It's Friday",
        "It's Satuday",
        "It's Sumday",
    ][day] ?? "Enter a value between 1 - 7";

2. Remove duplicate elements in an array

Duplicate elements in an array can be removed by Set constructor and spread syntax. Set constructor converts an array into a set which cannot have duplicate elements. Spread syntax can be used to convert the set object back to an array.

const array = [1,2,2,3,4,5]
const uniq = [...new Set(array)];
console.log(uniq) // [1,2,3,4,5]

3. Computed property names

You cannot set object keys as variables directly. It will read the variable names as key names.

const key1 = "name";
const key2 = "age";
const student = {
    key1:"john Doe",
    key2:26
}
console.log(student)
//{ key1:"john Doe", key2:26 }

Starting with ECMAScript 2015, you can put an expression in brackets [], that will be computed and used as the property name.

const key1 = "name";
const key2 = "age";
const student = {
    [key1]:"john Doe",
    [key2]:26
}
console.log(student)
//{ name:"john Doe", age:26 }

4. Prevent falsey value from evaluating to false

There are six falsey values in JavaScript: undefined, null, NaN, 0, "" (empty string), and false. A falsy value is something which evaluates to FALSE, for instance when checking a variable. There could be scenarios where you wont want a falsy value to evaluate to false.

const number = 5;
if(number){
    console.log('The number exists')
}else{
    console.log('The number do not exist')
}

Will print The number exists. But

const number = 0;
if(number){
    console.log('The number exists')
}else{
    console.log('The number do not exist')
}

Will print The number do not exists. This can be handled by giving an exception at the evaluation

const number = 0;
if(number===0?true:number){
    console.log('The number exists')
}else{
    console.log('The number do not exist')
}

Will print The number exists. 0 at the expression can be changed with any of the falsy values.