Dogfalo/materialize · error · Error

noUiSlider: 'behaviour' must be a string containing options.

Error message

noUiSlider: 'behaviour' must be a string containing options.

What it means

noUiSlider requires the 'behaviour' option to be a string of space-or-comma separated keywords (tap, drag, fixed, snap, hover). The guard rejects any non-string before parsing keywords, because indexOf would otherwise throw or misbehave.

Source

Thrown at extras/noUiSlider/nouislider.js:670

        // Invert connection for RTL sliders, so that the proper
        // handles get the connect/background classes.
        switch ( entry ) {
            case 'ltr':
                parsed.dir = 0;
                break;
            case 'rtl':
                parsed.dir = 1;
                break;
            default:
                throw new Error("noUiSlider: 'direction' option was not recognized.");
        }
    }

    function testBehaviour ( parsed, entry ) {

        // Make sure the input is a string.
        if ( typeof entry !== 'string' ) {
            throw new Error("noUiSlider: 'behaviour' must be a string containing options.");
        }

        // Check if the string contains any keywords.
        // None are required.
        var tap = entry.indexOf('tap') >= 0;
        var drag = entry.indexOf('drag') >= 0;
        var fixed = entry.indexOf('fixed') >= 0;
        var snap = entry.indexOf('snap') >= 0;
        var hover = entry.indexOf('hover') >= 0;

        if ( fixed ) {

            if ( parsed.handles !== 2 ) {
                throw new Error("noUiSlider: 'fixed' behaviour must be used with 2 handles");
            }

            // Use margin to enforce fixed state
            testMargin(parsed, parsed.start[1] - parsed.start[0]);

View on GitHub (pinned to 824e78248b)

Solutions

1. Pass behaviour as a single string containing the desired flags, e.g. 'tap drag' or 'drag-tap'.
2. If you have an array of flags, join them: behaviour: flags.join(' ').
3. Omit behaviour to use the default, or set it to an empty string '' if no flags are wanted.

Example fix

// before
noUiSlider.create(el, { start: 0, range:{min:0,max:100}, behaviour: ['tap','drag'] });
// after
noUiSlider.create(el, { start: 0, range:{min:0,max:100}, behaviour: 'tap drag' });

function normalizeBehaviour(raw) {
  if (Array.isArray(raw)) return raw.join(' ');
  if (typeof raw !== 'string') throw new TypeError('behaviour must be a string');
  return raw;
}

function isValidBehaviour(v) { return typeof v === 'string'; }

When it happens

Trigger: Call noUiSlider.create() with options.behaviour that is not a string: a boolean true, an array ['tap','drag'], an object, undefined-coerced, or null.

Common situations: Developers pass an array thinking behaviour accepts multiple flags as a list, or pass true/false expecting a boolean toggle. Also happens when behaviour is loaded from JSON where it was serialized as an array.

Related errors

• noUiSlider: 'padding' option must be less than half the rang
• noUiSlider: 'direction' option was not recognized.
• noUiSlider: 'fixed' behaviour must be used with 2 handles
• noUiSlider: must pass a formatter for all handles.
• noUiSlider: 'tooltips' must be passed a formatter or 'false'

AI-assisted analysis of Dogfalo/materialize@824e78248b (2026-08-13). Data as JSON: /api/errors/c7ff1e24a8008439. Report an issue: GitHub.