JavaScript helper: getMaxLengthString [TypeScript]

Here’s a quick JavaScript helper snippet to return a trimmed string based on the calculated maximum length of a string to fit the width of a parent container element.

Written in TypeScript.

/**
 * Takes a full string and returns a trimmed version to fit within a parent space.
 * @param fullLengthString  The full length string to trim to a parent space.
 * @param font              String representing the font styling of the text (required to calculate text length).
 * @param maxLengthPixels   Max pixel width of the parent space to fit the text into.
 * @param removeExtraChars  The number of extr characters to remove from the trimmed space, if required. (Default: 0)
 */
private getMaxLengthString(fullLengthString: string, font: string, maxLengthPixels: number, removeExtraChars: number = 0): string {
	let maxLengthString: string = "";

	let canvas = document.createElement("canvas");
	let context = canvas.getContext("2d");
	context.font = font;

	for (let i = 0; i < fullLengthString.length; i++) { // Build the string maxLengthString = maxLengthString + fullLengthString.charAt(i); // Test the length of the string let metrics = context.measureText(maxLengthString); if (metrics.width > maxLengthPixels) {
			// Trim the string to a max length.

			// The number of characters to remove.
			let removeChars = 1;   // At this point the length is too long, so remove 1 character to get it under.
			if (removeExtraChars > 0) {
				removeChars = removeChars + removeExtraChars;
			}
			removeChars = removeChars * -1; // To make sure they're sliced from the end.

			// Remove characters from the string.
			maxLengthString = maxLengthString.slice(0, removeChars);

			return maxLengthString;
		}
	}

	// Full string is OK.
	return maxLengthString;
}

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