How to generate all combinations of a string in JavaScript ?

We are going to see if we can generate all the possible combinations of a given string using JavaScript methods or concepts. You are given a string, containing different characters, you need to generate all combinations of a string by selecting a character at once and then re-arranging that character with other characters in such a way all the combinations could be generated and printed easily in our output.

Example:

Dog => Possible Combination [D], [Do], [Dog], [o], [og], [g]

Following are the several approaches to generate all the combinations of a string in JavaScript:

Approach 1: Use .push() and .slice() method

• In this approach, we will use the data structure called an array and will run two for loops on the given string which is the main logical part of our code
• Further, we will use .push() and .slice() methods to add our result to an array.

Example: This example shows the use of the above-explained approach.

Javascript

let possibleCombinations = (str) => {
    let combinations = [];
    for (let i = 0; i < str.length; i++) {
        for (let j = i + 1; j < str.length + 1; j++) {
            combinations.push(str.slice(i, j));
        }
    }
    return combinations;
}
console.log(possibleCombinations('Dog'));

Output

[ 'D', 'Do', 'Dog', 'o', 'og', 'g' ]

Approach 2: Using the .charAt() and .concat() method

• In this approach, we will again be using an array as our result printing variable and we will take our current index value as starting value (which is 0).
• Then we will run a while loop and inside that while loop we will store our character present at our current index value using the .charAt() method.
• Then we will declare a temporary array in which we will store that character obtained.
• Then we will run a for-in loop where in we will push our result and thereafter we will add our result in the result variable using the .concat() method and we will then increment our current index variable value.

Example: This example shows the use of the above-explained approach.

Javascript

let stringCombinations = (str) => {
    let strLength = str.length;
    let result = [];
    let currentIndex = 0;
    while (currentIndex < strLength) {
        let char = str.charAt(currentIndex);
        let x;
        let arrTemp = [char];
        for (x in result) {
            arrTemp.push("" + result[x] + char);
        }
        result = result.concat(arrTemp);
        currentIndex++;
    }
    return result;
};
console.log(stringCombinations("dog"));

Output

[
  'd',   'o',
  'do',  'g',
  'dg',  'og',
  'dog'
]

Approach 3: Using for loop and .push() method

• In this approach, we will use two arrays one is temporary which will initially store our results and at the end, we will add our results in the second result array.
• Here we will use firstly a for loop and inside that, for loop, we will add each character of a string in the temporary array, and then we will take starting index value as 0.
• Then inside the for loop, we will use .push() method to push our result into the temporary array and increment the current index value.
• Then after the for loop, we will add the result into our result array from the temporary array and then print the result array.

Example: In this example, we are using for loop and .push() method

Javascript

let combinations = (str) => {
    let tempArr = [];
    let resultArr = [];
    for (let i = 0; i < str.length; i++) {
        tempArr = [str[i]];
        let index = 0;
        while (resultArr[index]) {
            tempArr.push("" + resultArr[index] + str[i]);
            index++;
        }
        resultArr = resultArr.concat(tempArr);
    }
    return resultArr;
};
console.log(combinations("dog"));

Output

[
  'd',   'o',
  'do',  'g',
  'dg',  'og',
  'dog'
]