How to append a dot at the beginning of a string in array-Javascript - Stack Overflow

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I have an array:

arr= ["abd","test","testss"];

I want to add dot in front of all the strings like:

arr= [".abd",".test",".testss"];

this failed:

arr.forEach(function(e){
  e.append(".")
})

how can I do this?

I have an array:

arr= ["abd","test","testss"];

I want to add dot in front of all the strings like:

arr= [".abd",".test",".testss"];

this failed:

arr.forEach(function(e){
  e.append(".")
})

how can I do this?

• javascript

Share Improve this question Follow asked Oct 10, 2018 at 23:09 user1234user1234 3,15966 gold badges5757 silver badges117117 bronze badges 2

• Have a look at developer.mozilla/en-US/docs/Web/JavaScript/Reference/… and developer.mozilla/en-US/docs/Learn/JavaScript/First_steps/… – Felix Kling Commented Oct 10, 2018 at 23:13
• FWIW, strings are immutable in JavaScript, i.e. any operation you can do on a string produces a new string value that you have to assign to something. – Felix Kling Commented Oct 10, 2018 at 23:15

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6 Answers 6

Sorted by: Reset to default 2

You could use the map() method on the array type to achieve this:

var arr = ["abd","test","testss"];

// Iterate each string of arr, add a '.' to the start, 
// and return a copy of the updated array
arr = arr.map(function(value) { return '.' + value; })
    
console.log(arr)

If you're working with a fairly modern browser, you could also take advantage of modern syntax to achieve the same result via the following:

var arr = ["abd","test","testss"];

// Iterate each string of arr, add a '.' to the start, 
// and return a copy of the updated array
arr = arr.map(value => `.${value}`)
    
console.log(arr)

You can use Array.map API, like this -

arr= ["abd","test","testss"];

console.log(arr.map(item => `.${item}` ))

You can use array.map to do this. Array.map would let you travere the elements and returns an array. Here is the following snippet

let arr= ["abd","test","testss"];
arr = arr.map(item=> `.${item}`);
console.log(arr);

One way to do it is to use all the parameters provided by forEach, which are (1) the value of current element, (2) the index of the current element, (3) the array reference itself. Translated into code that would mean:

let arr = ['abc', 'def', 'ghi']

arr.forEach(function(value, index, array) {
    array[index] = '.' + value
});

// arr = ['.abc', '.def', '.ghi']

I am sure that there is a faster and possibly shorter way to do it, but hey it's something.

Assuming the strings don't have special chars, you can join and split.

let arr = ["abd", "test", "testss"];
console.log(("." + arr.join('|.')).split('|'));

.as-console-wrapper { max-height: 100% !important; top: 0; }

This is for backward patibility, without using transpilation.

var arr = ['a', 'b', 'c', 'd', 'e'];

for(var i = 0; i < arr.length; i++)
    arr[i] = '.' + arr[i];

console.log(arr); // ['.a', '.b', '.c', '.d', '.e']

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