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Dynamic from fields using reactive forms in Angular?

I have a scenario like Need to edit the single quotes values (only single quotes values),
So I extracted the single quotes values using regex and prepare the reactive dynamic form.
onclick of performing edit button will show old step name above, new step name below, submit step will replace the step name in the original array.
WOrking fine as expected in few scenarios according to my approach, but in scenarios, I realized whatever algorithm I am following does not fulfill my requirement.
Below are the test cases
Test case 1:
Step Name: "Then I should hire an employee using profile '1' for 'USA'",
// Here --> '1', 'USA' values are editable
Test case 2: "And Employee should be hired on '01' day of pay period '01' of 'Current' Fiscal"
// '01', '01', 'Current'
Issues: in test case 2 if I tried to edit second 01 it is editing the first 01
I try to solve the perform edit function with help of indexof, substring functions
this.replaceString = this.selectedStep.name;
this.metaArray.forEach((element: any) => {
var metaIndex = this.replaceString.indexOf(element.paramValue);
if (metaIndex !== -1) {
const replaceValue = this.stepEditForm.controls[element['paramIndex']].value;
this.replaceString = this.replaceString.substring(0, metaIndex) + replaceValue + this.replaceString.substring(metaIndex + (element.paramValue.length));
}
});
but in indexof always find the first occurrence of a value in a string. So I realized my approach is wrong on performed it function
please find the attachment for the code
https://stackblitz.com/edit/angular-reactive-forms-cqb9hy?file=app%2Fapp.component.ts
So Can anyone please suggest to me how to solve this issue,
Thanks in advance

I added a function called matchStartingPositions that returns the starting position indexes of each match. Using this method you can then perform your edit by replacing the string just as you do, but we'll find the proper match to be replaced at the given position.
So in your line
var metaIndex = this.replaceString.indexOf(element.paramValue);
we can then add a second parameter to indexOf, that is the starting point:
var metaIndex = this.replaceString.indexOf(element.paramValue, startingPositions[element.paramIndex]);
The function for getting the index positions just looks for those single quotes in a given string:
matchStartingPositions(str) {
let count = 0;
let indices = [];
[...str].forEach((val, i) => {
if (val === "'") {
if (count % 2 == 0) {
indices.push(i);
}
count++;
}
});
return indices;
}
Here it is in action:
https://angular-reactive-forms-xhkhmx.stackblitz.io
https://stackblitz.com/edit/angular-reactive-forms-xhkhmx?file=app/app.component.ts

Javascript Math.log() help wanted

World!
I'm trying to create a program in Javascript that takes the log of a number typed into an HTML input. Unfortunately i've encountered a problem where it wont accept the string with the .replace().
Its Function:
I.E: When log(10) is calculated, the function should first remove the first 4 char's "log(" next remove the last parenthesis ")" and then take the log of the no. between.
HTML includes style elements, button and input form and an output < DIV >.
//Function
function calculate()
{
var inputString = document.getElementById("inpstr");
var output = document.getElementById("output");
//TESTING CODE
/*
if (inputString.value.startsWith("log(").endsWith(")"))
{
console.log(output.innerHTML = inputString.value.substring(4, 20).replace(")", ""));
}
else
{
output.innerHTML = "false";
}
*/
//Math.log() calc *****DOESNT WORK*****
if (inputString.value.startsWith("log(").endsWith(")"))
{
output.innerHTML = Math.log(inputString.value.replace(")", "").substring(4, 20));
}
else
{
output.innerHTML = inputString.value;
}
event.preventDefault();
}
If someone can give me an effective solution that would be much appreciated.
Thanks,
Syntax

Since Math.log() accepts only number values and you're trying to pass a string to it, you should first parse this value into a float number and then pass it to the log function:
let val = parseFloat(inputString.value.replace(")", "").substring(4, 20));
output.innerHTML = Math.log(val);

I'm guessing I got downvoted for being lazy, so here is the quick info. Gonras got it right relating to what you want to extract, but he forgot to check that what's being input is actually a log.
That's where the regex below comes in handy! I'm matching the field to:
^ start of word, since we want to match the entire field.
log(
([-.\d])) any consecutive sequence () of numbers (\d), -, and '.', represented by the []. The \(...\) makes sure to save this inner part for later.
$ is end of word, see 1.
res will be null if there is no match. Otherwise, res[0] is the entire match (so the entire input field) and res[1] is the first 'capture group', at point 3 - which is presumably the number.
This of course fails for multiple "-" inside, or "." etc... so think it over.
//Function
function calculate()
{
var inputString = document.getElementById("inpstr");
var output = document.getElementById("output");
var res = /^log\(([-.\d]*)\)$/.exec(inputString.value);
if (res)
output.innerHTML = Math.log(res[1]);
else
output.innerHTML = res;
}
document.getElementById("output").innerHTML='start';
calculate()
<div id='output'></div>
<input id='inpstr' value='log(2.71828)'></input>
If I wanted to fix your if to supplement Gonras's solution:
if (inputString.value.startsWith("log(") && inputString.value.endsWith(")"))
Yours fails since startsWith() returns a boolean, which obviously doesn't have a endsWith function.

how to remove the last character of an input field using AngularJS

The title of this question is probably wrong, but i can't think of how to name it.
I'm trying to build a simple calculator using AngularJS. Right now its functioning, but i'm trying to add some other buttons. I want a "delete" key and a decimal key. The delete key is what i'm focused on now.
If someone clicks, 3, then 3 again. we have 33. (this calculator currently, can only accept a left and right operand, and an operator separating them (ex, 3+3, or 56*486, etc). not multiple operators or operands). Now say the user were to enter 334, but they want the 4 taken off because they meant to click 5. How do I use javascript to delete the most recent number if an operator or equals hasn't been pressed?
If i had to guess, it's going to be something like this:
$scope.deleteNumb = function(d){
if(!$scope.operator){
// if no operator, delete most recent left operand
}
else{ //delete most recent right operand}
}
};
The "C" button doesn't work. I had that set up as "Clear" which refreshed the page to start a new calculation. I need a way to figure out how to delete the existing answer without using location.reload();
So the main thing here, is trying to delete the recent most operand, whether it be left or right, depending if an operator has been clicked or not.
My code is here:
https://codepen.io/tevon/pen/Moewba

For clear (C) did you try to clear all values in setClear
$scope.setClear = function (a) {
$scope.leftOperand = "";
$scope.operator = "";
$scope.rightOperand = "";
$scope.answer = "";
};

to delete a part of your number; have a look to substr as your input is a string :
For exemple :
$scope.removeBtn = function(){
var tmp = $scope.leftOperand;
console.warn("test",tmp)
$scope.leftOperand = tmp.substr(0,tmp.length-1);
}
This function removes the last number of your leftOperand.
Adapt it to your need for left/right

$scope.setClear = function (a) {
// $scope.clear = location.reload();
var result = $scope.leftOperand + $scope.operator + $scope.rightOperand;
result = result.substring(0, result.length - 1);
if ($scope.operator){
$scope.rightOperand = result;
}
else {
$scope.leftOperand = result;
}
};
Not tested.. Would have to tweak a little when operators come i guess

Unable to Get Output From While Loop in Javascript

I'm working on my final project of the Winter 2017 quarter to demonstrate how to use Regular Expressions in both C# and JavaScript code behind pages. I've got the C# version of my demonstration program done, but the JavaScript version is making me pull what little hair I have left on my head out (no small achievement since I got a fresh buzz cut this morning!). The problem involves not getting any output after applying a Regular Expression in a While loop to get each instance of the expression and printing it out.
On my HTML page I have an input textarea, seven radio buttons, an output textarea, and two buttons underneath (one button is to move the output text to the input area to perform multiple iterations of applying expressions, and the other button to clear all textareas for starting from scratch). Each radio button links to a function that applies a regular expression to the text in the input area. Five of my seven functions work; the sixth is the one I can't figure out, and the seventh is essentially the same but with a slightly different RegEx pattern, so if I fix the sixth function, the seventh function will be a snap.
(I tried to insert/upload a JPG of the front end, but the photo upload doesn't seem to be working. Hopefully you get the drift of what I've set up.)
Here are my problem children from my JS code behind:
// RegEx_Demo_JS.js - code behind for RegEx_Demo_JS
var inputString; // Global variable for the input from the input text box.
var pattern; // Global variable for the regular expression.
var result; // Global variable for the result of applying the regular expression to the user input.
// Initializes a new instance of the StringBuilder class
// and appends the given value if supplied
function StringBuilder()
{
var strings = [];
this.append = function (string)
{
string = verify(string);
if (string.length > 0) strings[strings.length] = string;
}
this.appendLine = function (string)
{
string = verify(string);
if (this.isEmpty())
{
if (string.length > 0) strings[strings.length] = string;
else return;
}
else strings[strings.length] = string.length > 0 ? "\r\n" + string : "\r\n";
}
this.clear = function () { strings = []; };
this.isEmpty = function () { return strings.length == 0; };
this.toString = function () { return strings.join(""); };
var verify = function (string)
{
if (!defined(string)) return "";
if (getType(string) != getType(new String())) return String(string);
return string;
}
var defined = function (el)
{
// Changed per Ryan O'Hara's comment:
return el != null && typeof(el) != "undefined";
}
var getType = function (instance)
{
if (!defined(instance.constructor)) throw Error("Unexpected object type");
var type = String(instance.constructor).match(/function\s+(\w+)/);
return defined(type) ? type[1] : "undefined";
}
}
Within the code of the second radio button (which will be the seventh and last function to complete), I tested the ScriptBuilder with data in a local variable, and it ran successfully and produced output into the output textarea. But I get no output from this next function that invokes a While loop:
function RegEx_Match_TheOnly_AllInstances()
{
inputString = document.getElementById("txtUserInput").value;
pattern = /(\s+the\s+)/ig; // Using an Flag (/i) to select either lowercase or uppercase version. Finds first occurrence either as a standalone word or inside a word.
//result = pattern.exec(inputString); // Finds the first index location
var arrResult; // Array for the results of the search.
var sb = getStringBuilder(); // Variable to hold iterations of the result and the text
while ((arrResult = pattern.exec(inputString)) !==null)
{
sb.appendLine = "Match: " + arrResult[0] ;
}
document.getElementById("txtRegExOutput").value = sb.toString();
/* Original code from C# version:
// string pattern = #"\s+(?i)the\s+"; // Same as above, but using Option construct for case insensitive search.
string pattern = #"(^|\s+)(?i)the(\W|\s+)";
MatchCollection matches = Regex.Matches(userTextInput, pattern);
StringBuilder outputString = new StringBuilder();
foreach (Match match in matches)
{
string outputRegExs = "Match: " + "\"" + match.Value + "\"" + " at index [" + match.Index + ","
+ (match.Index + match.Length) + "]" + "\n";
outputString.Append(outputRegExs);
}
txtRegExOutput.Text = outputString.ToString();
*/
} // End RegEx_Match_The_AllInstances
I left the commented code in to show what I had used in the C# code behind version to illustrate what I'm trying to accomplish.
The test input/string I used for this function is:
Don’t go there. If you want to be the Man, you have to beat The Man.
That should return two hits. Ideally, I want it to show the word that it found and the index where it found the word, but at this point I'd be happy to just get some output showing every instance it found, and then build on that with the index and possibly the lastIndex.
So, is my problem in my While loop, the way I'm applying the StringBuilder, or a combination of the two? I know the StringBuilder code works, at least when not being used in a loop and using some test data from the site I found that code. And the code for simply finding the first instance of "the" as a standalone or inside another word does work and returns output, but that doesn't use a loop.
I've looked through Stack Overflow and several other JavaScript websites for inspiration, but nothing I've tried so far has worked. I appreciate any help anyone can provide! (If you need me to post any other code, please advise and I'll be happy to oblige.)

Javascript RegEx Help

I want to take strings like:
Submit Changes
Create New
Update Record
Save Item
and convert them to:
Submitting Changes
Creating New
Updating Record
Saving Item
with a function like:
var ConvertToProgressivePresent = (function(){
// cache this regex
var rProgressivePresent = /\b(?:(Submi(t))|(Creat|Sav|Updat)e)\b/i;
return function(phrase){
return phrase.replace(rProgressivePresent, "$1$2$3ing");
};
}());
This above regex works but doesn't seem like the best way to do it. I don't like the grouping here where 1-2 groups are always empty when there is a match.
Got any suggestions or improvements?

If you have specific words to replace with then you could make a word bank. Have the words and their replacement stored in an object and then loop through it.
var ConvertToProgressivePresent = (function() {
var replaceValues = {
"Submit": "Submitting",
"Create": "Creating",
"Update": "Updating",
"Save": "Saving"
}
return function(phrase) {
for (var item in replaceValues) {
phrase = phrase.replace(item, replaceValues[item]);
}
return phrase;
};
}());
Here is a JSFiddle Example

I think you should probablly use CASE statments instead. Regex isn't the most efficient way of doing things...and that is probably best that it doesn't cuz you know the old saying.
Wow, I have this problem...I know, I'll use regex...ok, now you have two problems 90)

First off, it doesn't appear to me that your regex does quite what you want anyway in that I don't see a second "t" added when changing submit to submitting.
However, I don't think I would use regex for this task at all anyway. If you are just trying to replace one word with another, and the word always comes at the beginning of the string, I might do something like:
function ReplaceIfBeginsWith(wholeString, checkFor, replaceWith)
{
if (wholeString.indexOf(checkFor + ' ') == 0)
{
return replaceWith + ' ' + wholeString.substr(checkFor.length + 1);
}
if (wholeString == checkFor)
{
return replaceWith;
}
return wholeString;
}
Then, you can call the function with each of the words you would want to replace. If you want case-insensitivity, just check against lowercase versions of all the strings.