Develop Reference

How to get characters from a text like LEFT() but using google apps script [duplicate]

This may duplicate with previous topics but I can't find what I really need.
I want to get a first three characters of a string. For example:
var str = '012123';
console.info(str.substring(0,3)); //012
I want the output of this string '012' but I don't want to use subString or something similar to it because I need to use the original string for appending more characters '45'. With substring it will output 01245 but what I need is 01212345.

var str = '012123';
var strFirstThree = str.substring(0,3);
console.log(str); //shows '012123'
console.log(strFirstThree); // shows '012'
Now you have access to both.

slice(begin, end) works on strings, as well as arrays. It returns a string representing the substring of the original string, from begin to end (end not included) where begin and end represent the index of characters in that string.
const string = "0123456789";
console.log(string.slice(0, 2)); // "01"
console.log(string.slice(0, 8)); // "01234567"
console.log(string.slice(3, 7)); // "3456"
See also:
What is the difference between String.slice and String.substring?

add an element "/" in particular position in string with Javascript

I want to add an element "/" within a string, but only a specific position of it, e.g. from string "20180101" to expect result like "2018/01/01".is anyone know what syntax or how to make it happen.I'm still beginner in javascript
any help would be really appreciate.

Here is one option using replace with a regex pattern:
var input = "20180419";
console.log(input.replace( new RegExp("^(\\d{4})(\\d{2})(\\d{2})", "gm"),"$1/$2/$3"));

Use substr approach to get the result:
var str = "20180101";
str = str.substr(0, str.length-4) + '/' + str.substr(4, str.length);
str = str.substr(0, str.length-2) + '/' + str.substr(7, str.length);;
console.log(str);

Another option creating an array of sub-strings with slice (note that this would work the same way with substring here), and then joining each part with a /:
let s = "20180101"
let result = [s.substring(0,4), s.substring(4,6), s.substring(6,8)].join('/')

In such cases, you may find useful to treat your string as an array of digits.
Get an array of digits from your string:
let myString = '20180101';
let myArray = myString.split('') //the '' splitter means it will just split anything
Then, add into your array of digits, the desired '/' digit in the desired positions. Refer to the splice method for more information.
myArray.splice(4,0,'/');
myArray.splice(7,0,'/');
Then, build your string:
myString = myArray.join(''); //the opposite of splitting
console.log(myString) // outputs '2018/01/01'

Javascript to cut same second character on a text

For example I have text:
var x="default_1305, default_1695, default_1805";
I want to cut before the second comma to get this text:"default_1305, default_1695".
How can I do this?

var x="default_1305, default_1695, default_1805";
string can be split by , like below:
var res = x.split(",", 2);
Note 2 here in the second param.
And if needed as string, then
var res_string = res.join(",");
Edit:
.split() on MDN
Syntax
str.split([separator[, limit]])
Parameters
separator
Optional. Specifies the character(s) to use for separating the string. The separator is treated as a string or a regular expression. If separator is omitted, the array returned contains one element consisting of the entire string. If separator is an empty string, str is converted to an array of characters.
limit
Optional. Integer specifying a limit on the number of splits to be found. The split() method still splits on every match of separator, until the number of split items match the limit or the string falls short of separator.

Convert string to array and get first two elements
var x="default_1305, default_1695, default_1805";
var b = x.split(',')
var c = b[0]+","+b[1]

You can also use .slice() to get the parts you need, eg:
// added an extra item to distinguish first-two vs all-but-last
var x="default_1305, default_1695, default_1805, default_1962";
// get first two
var result = x.split(",").slice(0,2).join(",");
console.log(result);
// get all but last
var result = x.split(",").slice(0,-1).join(",");
console.log(result);

String split returns an array with more elements than expected (empty elements)

I don't understand this behaviour:
var string = 'a,b,c,d,e:10.';
var array = string.split ('.');
I expect this:
console.log (array); // ['a,b,c,d,e:10']
console.log (array.length); // 1
but I get this:
console.log (array); // ['a,b,c,d,e:10', '']
console.log (array.length); // 2
Why two elements are returned instead of one? How does split work?
Is there another way to do this?

You could add a filter to exclude the empty string.
var string = 'a,b,c,d,e:10.';
var array = string.split ('.').filter(function(el) {return el.length != 0});

A slightly easier version of #xdazz version for excluding empty strings (using ES6 arrow function):
var array = string.split('.').filter(x => x);

This is the correct and expected behavior. Given that you've included the separator in the string, the split function (simplified) takes the part to the left of the separator ("a,b,c,d,e:10") as the first element and the part to the rest of the separator (an empty string) as the second element.
If you're really curious about how split() works, you can check out pages 148 and 149 of the ECMA spec (ECMA 262) at http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-262.pdf

Use String.split() method with Array.filter() method.
var string = 'a,b,c,d,e:10.';
var array = string.split ('.').filter(item => item);
console.log(array); // [a,b,c,d,e:10]
console.log (array.length); // 1

https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/String/split
trim the trailing period first
'a,b,c,d,e:10.'.replace(/\.$/g,''); // gives "a,b,c,d,e:10"
then split the string
var array = 'a,b,c,d,e:10.'.replace(/\.$/g,'').split('.');
console.log (array.length); // 1

That's because the string ends with the . character - the second item of the array is empty.
If the string won't contain . at all, you will have the desired one item array.
The split() method works like this as far as I can explain in simple words:
Look for the given string to split by in the given string. If not found, return one item array with the whole string.
If found, iterate over the given string taking the characters between each two occurrences of the string to split by.
In case the given string starts with the string to split by, the first item of the result array will be empty.
In case the given string ends with the string to split by, the last item of the result array will be empty.
It's explained more technically here, it's pretty much the same for all browsers.

According to MDN web docs:
Note: When the string is empty, split() returns an array containing
one empty string, rather than an empty array. If the string and
separator are both empty strings, an empty array is returned.
const myString = '';
const splits = myString.split();
console.log(splits);
// ↪ [""]

Well, split does what it is made to do, it splits your string. Just that the second part of the split is empty.

Because your string is composed of 2 part :
1 : a,b,c,d,e:10
2 : empty
If you try without the dot at the end :
var string = 'a,b,c:10';
var array = string.split ('.');
output is :
["a,b,c:10"]

You have a string with one "." in it and when you use string.split('.') you receive array containing first element with the string content before "." character and the second element with the content of the string after the "." - which is in this case empty string.
So, this behavior is normal. What did you want to achieve by using this string.split?

try this
javascript gives two arrays by split function, then
var Val = "abc#gmail.com";
var mail = Val.split('#');
if(mail[0] && mail[1]) { alert('valid'); }
else { alert('Enter valid email id'); valid=0; }
if both array contains length greater than 0 then condition will true

Trim string, but return the number of spaces removed from the start

I need to find out how many characters were removed from the start of the string, which is the value of a textarea input, so I can determine the new start position of the cursor selection.
$.trim() will do the trim, but how can I find out how many chars were taken from the start?

Use the indexOf() method to find the occurance of the trimmed version in the original string.
var string = " aaa";
var trimmed = $.trim(string); // aaa;
var diff = string.indexOf(trimmed); // 2;
You cannot simply compare the lengths, as spaces may have been trimmed from the end of the string.

Something like this will do the trick
var numberOfStartWS = yourOrigString.match(/^(\s*)/)[1].length;

The difference between the lengths of the trimmed string and the non-trimmed string will be the number of characters that were trimmed.

Cant you take the length of the string before you trim and then do a diff between the new trimmed string?