String Functions

This document covers JavaScript String functions available in Ensemble with examples. Each function is briefly explained and followed by an example demonstrating its usage.

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length

The length property returns the length of the string

Example:

var str = "Hello";
var len = str.length;
console.log(len); // 5

indexOf

The indexOf() method returns the index of the first occurrence of the specified value in a string.

Example:

var str = "Hello, world!";
var index = str.indexOf("world");
console.log(index); // 7

lastIndexOf

The lastIndexOf() method returns the index of the last occurrence of the specified value in a string.

Example:

var str = "Hello, world! world!";
var index = str.lastIndexOf("world");
console.log(index); // 14

charAt

The charAt() method returns the character at the specified index in a string.

Example:

var str = "Hello, world!";
var char = str.charAt(7);
console.log(char); // 'w'

endsWith

The endsWith() method determines whether a string ends with the characters of a specified string.

Example:

var str = "Hello, world!";
var result = str.endsWith("world!");
console.log(result); // true

includes

The includes() method determines whether a string contains the characters of a specified string.

Example:

var str = "Hello, world!";
var result = str.includes("world");
console.log(result); // true

toLowerCase

The toLowerCase() method returns the calling string value converted to lowercase.

Example:

var str = "Hello, World!";
var lowerCaseStr = str.toLowerCase();
console.log(lowerCaseStr); // "hello, world!"

toUpperCase

The toUpperCase() method returns the calling string value converted to uppercase.

Example:

var str = "Hello, World!";
var upperCaseStr = str.toUpperCase();
console.log(upperCaseStr); // "HELLO, WORLD!"

trim

The trim() method removes whitespace from both ends of a string.

var str = "   Hello, world!   ";
var result = str.trim();
console.log(result); // "Hello, world!"

trimStart

The trimStart() method removes whitespace from the beginning of a string.

var str = "   Hello, world!";
var result = str.trimStart();
console.log(result); // "Hello, world!"

trimEnd

The trimEnd() method removes whitespace from the end of a string.

var str = "Hello, world!   ";
var result = str.trimEnd();
console.log(result); // "Hello, world!"

repeat

The repeat() method constructs and returns a new string which contains the specified number of copies of the string on which it was called, concatenated together.

var str = "Hello ";
var result = str.repeat(3);
console.log(result); // "Hello Hello Hello "

search

The search() method executes a search for a match between a regular expression and this String object.

var str = "Hello, world!";
var result = str.search(/world/);
console.log(result); // 7

slice

The slice() method extracts a section of a string and returns it as a new string, without modifying the original string.

var str = "Hello, world!";
var result = str.slice(7, 12);
console.log(result); // "world"

substr

The substr() method returns a portion of the string, starting at the specified index and extending for a given number of characters afterward.

var str = "Hello, world!";
var result = str.substr(7, 5);
console.log(result); // "world"

match

The match() method retrieves the result of matching a string against a regular expression and returns null in case there is no match.

Example:

var str = "Hello, world!";
var regex = /world/;
var result = str.match(regex);
console.log(result); // "world"

matchAll

The matchAll() method returns an array of all the matched strings or an empty array in case there is no match.

Example:

var str = "Hello, world! world!";
var regex = /world/g;
var matches = str.matchAll(regex);
console.log(matches[0]); // "world"
console.log(matches[1]); // "world"

padStart

The padStart() method pads the current string with another string (multiple times, if needed) on the left until the resulting string reaches the given length.

If width is already smaller than or equal to this.length, no padding is added. A negative width is treated as zero.
The second argument (string to be padded with) is optional. When not specified, space is used for padding
If padding has length different from 1, the result will not have length width. This may be useful for cases where the padding is a longer string representing a single character, like " " or "\u{10002}". In that case, the user should make sure that this.length is the correct measure of the string's length.

Example:

var str = "world";
var paddedStr = str.padStart(6, "Hello");
console.log(paddedStr); // "Helloworld"
paddedStr = str.padStart(10, "Hello");
console.log(paddedStr); // "HelloHelloHelloHelloHelloworld"
paddedStr = str.padStart(8, "<");
console.log(paddedStr); // "<<<world"

padEnd

The padEnd() method pads the current string with another string (multiple times, if needed) on the right until the resulting string reaches the given length.

If width is already smaller than or equal to this.length, no padding is added. A negative width is treated as zero.
The second argument (string to be padded with) is optional. When not specified, space is used for padding
If padding has length different from 1, the result will not have length width. This may be useful for cases where the padding is a longer string representing a single character, like " " or "\u{10002}". In that case, the user should make sure that this.length is the correct measure of the string's length.

Example:

var str = "world";
var paddedStr = str.padEnd(6, "Hello");
console.log(paddedStr); // "worldHello"
paddedStr = str.padEnd(10, "Hello");
console.log(paddedStr); // "worldHelloHelloHelloHelloHello"
paddedStr = str.padEnd(8, "<");
console.log(paddedStr); // "world<<<"

replace

The replace() function replaces the first occurrence of a specified substring or regular expression with a new substring. It returns a new string with the replaced content while leaving the original string unchanged.

Syntax:

replace(pattern, replacement);

Example:

const p = 'The quick brown fox jumps over the lazy dog. If the dog reacted, was it really lazy?';
 
console.log(p.replace('dog', 'monkey'));
// Expected output: "The quick brown fox jumps over the lazy monkey. If the dog reacted, was it really lazy?"
 
const regex = /Dog/i;
console.log(p.replace(regex, 'ferret'));
// Expected output: "The quick brown fox jumps over the lazy ferret. If the dog reacted, was it really lazy?"

replaceAll

The replaceAll() method of String values returns a new string with all matches of a pattern replaced by a replacement. The pattern can be a string or a RegExp, and the replacement can be a string or a function to be called for each match. The original string is left unchanged.

Syntax:

replaceAll(pattern, replacement)

Example:

const p = 'The quick brown fox jumps over the lazy dog. If the dog reacted, was it really lazy?';
 
console.log(p.replaceAll('dog', 'monkey'));
// Expected output: "The quick brown fox jumps over the lazy monkey. If the monkey reacted, was it really lazy?"
 
// Global flag required when calling replaceAll with regex
const regex = /Dog/gi;
console.log(p.replaceAll(regex, 'ferret'));
// Expected output: "The quick brown fox jumps over the lazy ferret. If the ferret reacted, was it really lazy?"

split

The split() method divides a string into an ordered list of substrings, puts these substrings into an array, and returns the array.

Example:

var str = "Hello, world!";
var arr = str.split(", ");
console.log(arr); // ["Hello", "world!"]

startsWith

The startsWith() method determines whether a string begins with the characters of a specified string.

Example:

var str = "Hello, world!";
var result = str.startsWith("Hello");
console.log(result); // true

substring

The substring() method returns the part of the string between the start and end indexes, or to the end of the string.

Example:

var str = "Hello, world!";
var substr = str.substring(7, 12);
console.log(substr); // "world"

btoa

The btoa() method creates a base-64 encoded ASCII string from a string of binary data.

Example:

var str = "Hello, world!";
var base64 = btoa(str);
console.log(base64); // "SGVsbG8sIHdvcmxkIQ=="

atob

The atob() method decodes a base-64 encoded string, returning the original binary data.

Example:

var base64 = "SGVsbG8sIHdvcmxkIQ==";
var decodedStr = atob(base64);
console.log(decodedStr); // "Hello, world!"

tryParseInt

The tryParseInt() method parses as string as int and returns null if it is not an integer. `parseInt()' throws an error when the passed in argument cannot be parsed as an integer

Example:

var str = "123";
var i = str.tryParseInt(); // 123
str = "xyz";
i = tryParseInt(); // null

tryParseDouble

The tryParseDouble() method parses as string as double and returns null if it is not a double. `parseDouble()' throws an error when the passed in argument cannot be parsed as a double

Example:

var str = "123.05";
var i = str.tryParseDouble(); // 123.05
str = "xyz";
i = tryParseDouble(); // null

Concatenate a string in an inline expression

We can concatenate strings with variables or other strings simply by wrapping them in single quotes if the inner strings are wrapped in double quotes or vise versa. This example is specifically for inline expressions used in ensembleUI.

Example

Column:
  children:
    - Text:
        id: helloId
        text: Apple
    - Text:
        text: '${helloId.text + "It's me SwiftUI"}'     # correct way
    - Text:
        text: ${helloId.text} + It's me SwiftUI New     # wrong way
    - Text:
        text: Apple + It's me SwiftUI New 2

Numbers App object