Develop Reference

How to find whole substring in string?

I have a string and I have to check if that string contains defined substring I need to do some work and otherwise, I should return some error.
I have the following code:
function isContains(myString) {
let subString = 'test1234';
if(myString.includes(subString)) {
// to do some work
} else {
// return some error.
}
}
but the problem is if myString = 'my-string-test1-rrr' its condition return true.
How can I get true only in case when the whole subString was included in myString?

Use indexOf() instead.
function isContains(myString) {
let subString = 'test1234';
if(myString.indexOf(subString) > -1) {
// to do some work
} else {
// return some error.
}
}

you can use regex to check if that value is present are not;
example 1
without containing the specific string
var test = 'my-string-test1-rrr';
console.log(' test --- ', test.match(/test1234/g))
example 2
contains the specific string
var test = 'my-string-test1234-rrr';
console.log(' test --- ', test.match(/test1234/g))

It is highly recommended to use includes() over indexOf() and further indexOf returns the index of the occurrence where you would prefer an immediate answer - false / true if that substring is found inside the searched string.
Your function does exactly what you are asking. I would suggest to isolate the retrieval of this function and make it purer like so, then when you have the return boolean value you could utilize it after to run whatever logic you wish. This way you keep this function pure and separate your concerns better.
I also believe it would be easier for you to debug your issue if you isolate this functions like In the example I provided.
function isContains(myString) {
let subString = 'test1234';
let isContains = false;
if(myString.includes(subString)) {
isContains = true;
} else {
isContains = false;
}
return isContains;
}
You could use it like so in a later phase in your code:
const myString = 'my-string-test1-rrr';
let shouldRunOtherLogic = isContains(myString);
if (shouldRunOtherLogic) {
// to do some work
} else {
// return some error.
}
Hope I could help, if there's anything further you may need feel free to let me know.

Check if string is starting with prefix

I would like to check with javascript if array items starts with the word "prefix".
So far I've done something like this:
let array = ["prefix-word1", "prefix-word2"];
array.forEach(function(element) {
if (element.lastIndexOf('prefix', 0) == 0) {
console.log('prefix');
}
}
For some reason I keep get an error that prefix is not defined. Please help.

This one works (check the comments on the code):
let array = ["prefix-word1", "prefix-word2" , "does not start with prefix"];
array.forEach(function(element) {
// Check if the first word is prefix
if (element.indexOf('prefix') == 0) {
console.log('prefix');
console.log(element);
}
});
console.log("Second approach which is not suggested");
array.forEach(function(element) {
// not the correct approach as suggested by #Barmar though it works
if (element.lastIndexOf('prefix',0) == 0) {
console.log('prefix');
console.log(element);
}
});

Try using double quotation marks instead of single like this "prefix" in functions.

Is it correct to execute a function inside IF else statement?

The isCheck() function returns false if not radio buttons have been checked.
if (isCheck() === false) {
i = 0;
return i;
}

yes it works. alternatively you could use ternary operator
using that syntax:
test ? expression1 : expression2
for example :
//init var i with some value
var i = 1;
function isCheck(){ return false;}
i = isCheck() === false ? 0 : i;
return i;
or simple:
//before you should initialize i
return !isCheck() ? 0 : i ;

There is no wrong in executing a function inside if conditional statement.
For such case you can use ternary operator
var i=-1; // Note var key word & initialized with some value
isCheck() === false ? (i=0):(i=someOtherVal)

I don't see why not, some will say its not conventional but it should work just fine!

Yes it is correct
You dont need to create a variable only to receive a bool and later do a validation you can do directly.

logic error in javascript code

I am trying to write some logic that will check for the existence of a specific record in two tables.
If the row exists in either table, I want to return TRUE.
For table A, when the record is added to the table, the id field looks like "123".
For table B, the same record would have the id of "a123". However, the value i have to search for the record is "row_123".
This is what my code looks like right now :
var checkForDuplicates = function(row_id) {
return !!($('#existing_members').find('#' + row_id.replace('row_','')).length || $('#selected_users').find('#' + row_id.replace('row_','a').length) );
};
I want the function to return true if the record exists in either table.
However, this statement returns true in cases when it should be false.
What I've tried so Far
I've been playing around in the console to make sure that my logic is correct:
!!(1 || 0) //returns true
!!(0 || 0) //returns false
!!(0 || 1) //returns true
I'm also currently reviewing the replace statements to make sure the find() is being supplied the right strings.
But a second pair of eyes to confirm that my logic is correct would be appreciated.
Thanks
EDIT 1
The solution, using Max's suggestion would be:
var checkForDuplicates = function(row_id) {
var parts = row_id.split('_');
var tableB = '#a'+ parts[1];
var tableA = '#' + parts[1];
return !!($('#existing_members').find(tableA).length || $('#selected_users').find(tableB).length);
}
However, as Ankit points out, I just had a typo in my original code. So this would be my final answer / solution:
var checkForDuplicates(row_id) {
return !!( $('#existing_members').find('#' + row_id.replace('row_', '')).length || $('#selected_users').find('#' + row_id.replace('row_','a')).length);
}

Your code has a typo at the end of return statement
...'a').length)); //it returns object which always evaluates to true
it should be
...'a')).length);
DEMO
var checkforduplicates = function(row_id){
//row_id looks like "row_123"
return !!($('#tableA').find('#' + row_id.replace('row_','')).length || $('#tableB').find('#' + row_id.replace('row_','a')).length );
}
alert(checkforduplicates("row_123"));
<table id=tableA><tr><td id="123">123 ID</td></tr></table>
<table id=tableA><tr><td id="a13">a13 ID</td></tr></table>

Corrected few issues to make the code more efficient:
var checkforduplicates = function(row_id) {
var id = row_id.split('_')[1]; // [ 'row', '123']
return $('#'+id).length || $('#a'+id).length;
}
No need for !! as operator || produces boolean result (true or
false)
Used $('#'+id) as more efficient jQuery selector
Removed unnecessary find(..) call
Eliminated unnecessary parenthesis (which had an issue)

I want the function to return true if the record exists in either table.
var checkForDuplicates = function(row_id) {
row_id = row_id.substring(4); // 'row_123' -> '123'
var table_A_row_id = row_id;
var table_A_row_exists = $('#tableA').find('#' + table_A_row_id).length > 0;
var table_B_row_id = 'a' + row_id;
var table_B_row_exists = $('#tableB').find('#' + table_B_row_id).length > 0;
return table_A_row_exists || table_B_row_exists;
};

of course it is returning the opposite of the things you want, cause you are using !!.
! is used to negotiate the return value of the specific function/variable e.g.:
if(!var_x == false)
this example only works if var_x is true.
So please be aware to avoid !! ;)
Please use a single ! instead!

How to find if a value matches one of the values from an array in Javascript [duplicate]

This question already has answers here:
How do I check if an array includes a value in JavaScript?
(60 answers)
Closed 6 years ago.
FYI: this is for a simple quiz with just a single input field for each answer.
I have the following Javascript if statement to check if the value entered into an input field is correct (in this case, if the value entered is 'england').
$('input').keyup(function () {
if ($(this).val().toLowerCase() == 'england') {
//Stuff
} else {
//Other Stuff
};
});
However, I want to allow for alternative spellings, so I need a few possible answers for each question - it seems sensible to use an array for this as so...
var ans1 = new Array();
ans1[0] = "England";
ans1[1] = "Englund";
ans1[2] = "Ingland";
How can I change my if statement to say 'if the input field value equals any of those values from the array, then do the following'?
Any help would be greatly appreciated! Thank you.

You can do this using .inArray():
if ($.inArray($(this).val(), ans1) > -1) {
//Stuff
}
Here, the code $.inArray($(this).val(), ans1) will search for a specified value for example England within an array ans1 and return its index (or -1 if not found).
UPDATE
For case-sensitive search:
First enter all the values in the array in Lower Case
Next use the code below:-
JS:
if ($.inArray($(this).val().toLowerCase(), ans1) > -1) {
//Stuff
}

You can use the 'indexOf' method of the array, this will return -1 if the value doesn't exist in the array:
//if answer is in array
if(array.indexOf(answer) != -1){
//do stuff
}else{
//do stuff
}

Try this
if(this.value.match(/^(England|Englund|Ingland)$/i))
using regex and gi modifier for case insensitive

Do like this
$('input').keyup(function () {
var ans1 = new Array();
ans1[0] = "England";
ans1[1] = "Englund";
ans1[2] = "Ingland";
for(int i=0;i<ans1.length;i++)
{
if ($(this).val().toLowerCase() ==ans1[i]) {
//Stuff
} else {
//Other Stuff
};
}
});

Perhaps you may consider checking each element of the array like that:
var ans1 = new Array();
ans1[0] = "England";
ans1[1] = "Englund";
ans1[2] = "Ingland";
$('input').keyup(function () {
for (var i = 0; i < ans1.length; i++) {
if ($(this).val().toLowerCase() == ans1[i]) {
//Stuff
} else {
//Other Stuff
};
}
});
Not the most beautiful solution, but it should work.

jQuery offers $.inArray:
var found = $.inArray('specialword', words) > -1;
Note that inArray returns the index of the element found, so 0 indicates the element is the first in the array. -1 indicates the element was not found.
put your spellings in an array like this:
words: [
"England"
"Inglund"
"Ingland"
]
Found will be true if the word was found.
If you want the index of the matched word delete > -1 from the line.
Your code would be like this:
$('input').keyup(function () {
var found = $.inArray($(this).val(), words);
found > -1 ? //Stuff : //otherStuff;
});