How to describe the if condition in a more efficient way in JS?

user_4270155 0
Viewed 101

I am doing check on three different variables which are holding array of strings like below.

var a = ["ghi",dwe"]
var b = ["ghsj"]
var c = ["gdjr"]
var result; // result array

I am checking each time if variable a,b,c are not undefined and if they are holding some value I am simply pushing a string for each variable in the result array.

Below is line of code for same.

    if(a !== undefined && a.length > 0) {

    result.push("Astring");

}

if(b !== undefined && b.length > 0) {
    result.push("Bstring");

}

if(c!== undefined && c.length > 0) {
    result.push("Cstring");
}

Expected Result should be if the var a,b,c are defined and non empty then result array variable should hold value like below

["Astring","BString","CString"]

Is there a more efficient way of describing this code.Here I am just checking each and every variable using if condition. Also , I am restricted in some ways as I am using a Rhino js engine ver 1.7.12.

rhino if-statement arrays javascript
5 Answers

You could create an object with your initial data. Then iterate over it, and append the key (e.g. a, b or c) if it matches your condition.

Here's a quick demo:

// Initial Data
const a = ['ghi', 'dwe'];
const b = ['ghsj'];
const c = ['gdjr'];

// Store intial within an array
const abc = {a, b, c};

const result = [];

// Append each data item that present, is array, and not empty
Object.keys(abc).forEach((letterKey) => {
  const content = abc[letterKey];
  if(Array.isArray(content) && content.length > 0) {
    result.push(letterKey);
  }
});

// Print results
console.log(result);

user_9790520

I'd use an object instead of an array, so that the result-elements can be specified.

var a = ["ghi","dwe"]
var b = ["ghsj"]
var c = ["gdjr"]

mapping = {
    "AString": a,
    "BString": b,
    "CString": c
}
var result = []; // result array
for (let [key, value] of Object.entries(mapping)) {
    if (value !== undefined && value.length > 0) {
        result.push(key)
    }
}

console.log(result)

user_57106370

first you will store the 3 variables in a list then you loop over them with map

var a = ["ghi","dwe"]
var b = ["ghsj"]
var c = ["gdjr"]
var result = [];

let list = [a,b,c]

list.map(item => {
    if(item !== undefined && a.length > 0) {
        result.push(item)
    }
})
user_185877790

I think the most efficient way is a raw for loop.

var a = ["ghi","dwe"]
var b = ["ghsj"]
var c = ["gdjr"]
var result = [];

const items = [a,b,c]
const itemCount = items.length
let resultingItems = []
for (let i = 0; i < itemCount; i++) {
    if(items[i] !== undefined && items[i].length > 0) {
        resultingItems .push(items[i])
}

Raw for loop might be more efficient as the map function creates a new array populated with the results of calling a provided function on every element in the calling array.

user_118261320

I think the best way is for you to define a function:

var a = ["ghi","dwe"];
var b = [];
var c = ["gdjr"];
var result = [];

function pushToResult(variable, value){
  if(typeof variable != 'undefined' && variable.length > 0)
    result.push(value)
}

pushToResult(a, "Astring");
pushToResult(b, "Bstring");
pushToResult(c, "Cstring");

console.log(result);

If you want push the variable name into the result, then:

var a = ["ghi","dwe"];
var b = [];
var c = ["gdjr"];
var result = [];

function pushToResult(variable, value){
  if(typeof variable != 'undefined' && variable.length > 0)
    result.push(value)
}

pushToResult(a, Object.keys({a})[0]);
pushToResult(b, Object.keys({b})[0]);
pushToResult(c, Object.keys({c})[0]);

console.log(result);

user_53851350
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