<length-percentage>

This value specifies the width of the space the text will be adjusted to occupy as absolute length or percentage.

<number>

A numeric value outlines a length referring to the units of the current coordinate system.

Let's create a simple example that presents text you can resize using an <input> element of type "range".

Let's start with the SVG. It's pretty basic, with a 1000-by-300 pixel space mapped into a 10 centimeter by 3 centimeter box.

<svg
  width="10cm"
  height="3cm"
  viewBox="0 0 1000 300"
  xmlns="http://www.w3.org/2000/svg">
  <rect
    x="1"
    y="1"
    width="998"
    height="298"
    fill="none"
    stroke="green"
    stroke-width="2" />

  <text
    id="hello"
    x="10"
    y="150"
    font-family="sans-serif"
    font-size="60"
    fill="green">
    Hello world!
  </text>
</svg>

First, a <rect> element is used to create and stroke a rectangle to contain the text. Then <text> is used to create the text element itself, with an id of "hello".

The HTML is also simple, with only two displayed elements contained inside a grouping <div>:

<div class="controls">
  <input type="range" id="widthSlider" min="80" max="978" />
  <span id="widthDisplay"></span>
</div>

The <input> element, of type "range", is used to create the slider control the user will manipulate to change the width of the text. A <span> element of ID "widthDisplay" is provided to display the current width value.

Finally, let's have a look at the JavaScript code. It starts by stashing references to the elements it will need to access, using Document.getElementById():

const widthSlider = document.getElementById("widthSlider");
const widthDisplay = document.getElementById("widthDisplay");
const textElement = document.getElementById("hello");
const baseLength = Math.floor(textElement.textLength.baseVal.value);

widthSlider.value = baseLength;

widthSlider.addEventListener(
  "input",
  (event) => {
    textElement.textLength.baseVal.newValueSpecifiedUnits(
      SVGLength.SVG_LENGTHTYPE_PX,
      widthSlider.valueAsNumber
    );
    widthDisplay.innerText = widthSlider.value;
  },
  false
);

widthSlider.dispatchEvent(new Event("input"));

After fetching the element references, an EventListener is established by calling addEventListener() on the slider control, to receive any input events which occur. These events will be sent any time the slider's value changes, even if the user hasn't stopped moving it, so we can responsively adjust the text width.

When an "input" event occurs, we call newValueSpecifiedUnits() to set the value of textLength to the slider's new value, using the SVGLength interface's SVG_LENGTHTYPE_PX unit type to indicate that the value represents pixels. Note that we have to dive into textLength to get its baseVal property; textLength is stored as an SVGLength object, so we can't treat it like a plain number.

After updating the text width, the contents of the widthDisplay box are updated with the new value as well, and we're finished.

Here's what the example looks like. Try dragging the slider around to get a feel for what it does.

• SVG Tutorial: Texts
• SVGAnimatedLength and SVGLength
• <text>