The getSubStringLength() method of the SVGTextContentElement interface represents the computed length of the formatted text advance distance for a substring of text within the element.
Note that this method only accounts for the widths of the glyphs in the substring and any extra spacing inserted by the CSS letter-spacing and word-spacing properties. Visual spacing adjustments made by the x attribute are ignored.
getSubStringLength(index, length)indexAn integer; the start index of the substring.
lengthAn integer; the number of characters to include in the substring.
A float.
IndexSizeError DOMExceptionThrown if the index is greater than the highest index or length is negative.
<svg width="300" height="100">
<text id="exampleText" x="10" y="50" font-size="16">Hello, SVG World!</text>
</svg>const textElement = document.getElementById("exampleText");
// Get the length of a substring starting at character 0 with 5 characters
const substringLength = textElement.getSubStringLength(0, 5);
console.log(substringLength); // Output: 35.55