To convert user input string to regular expression with JavaScript, we use the RegExp constructor.
For instance, we write
const re = new RegExp("\\w+");
const matches = re.test("hello");
to call the RegExp constructor with the string with the pattern we want to match.
'\\w+' matches words.
Then we call re.test with the word we want to check if it matches.
To set focus on an element in an HTML form using JavaScript, we call the input’s focus method.
For instance, we write
<input type="text" id="myText" />
to add an input.
Then we write
document.getElementById("myText").focus();
to select the input with getElementById.
Then we call focus to set focus on it.
To disable input conditionally with Vue.js, we set the :disabled prop.
For instance, we write
<template>
<input type="text" :disabled="!validated" />
</template>
to set the disabled prop to the negation of the validated reactive property.
The input will then be disabled when validated is false.
To use moment.js to convert date to string in mm/dd/yyyy format with JavaScript, we use the format method.
For instance, we write
const startDate = moment().format("MM/DD/YYYY HH:mm:ss");
to create a moment object with moment with the current datetime.
Then we call format with a format string to return a string in mm/dd/yyyy format with the time in hours:minutes:seconds format.
To read in a local csv file in JavaScript, we can use the FileReader constructor.
For instance, we write:
<input type="file">
to add a file input.
Then we write:
const input = document.querySelector('input')
const fileReader = new FileReader()
fileReader.onload = (e) => {
console.log(e.target.result)
}
input.onchange = (e) => {
const [file] = e.target.files
fileReader.readAsBinaryString(file)
}
to select the input with querySelector.
Next, we create a FileReader instance.
Then we set its onload property to a function that logs the file content.
Next, we set input.onchange to a function that gets the selected file from e.target.files.
And then we call fileReader.readAsBinaryString to read the file.