plotly/plotly.js · warning

Variable '${key}' in ${name} could not be found! Please veri

Error message

Variable '${key}' in ${name} could not be found! Please verify that the template is correct. Using value: '${fallbackValue}'.

What it means

plotly.js's internal template-string helper substitutes placeholders like %{x} or ${key} in attribute strings. When a referenced variable is undefined, it warns that the variable could not be found and falls back to a fallback value (either the raw match or a caller-supplied fallback). This indicates a malformed or over-generic template rather than a fatal error.

Source

Thrown at src/lib/index.js:1143

                if (!obj) continue;
                if (obj.hasOwnProperty(key)) {
                    value = obj[key];
                    break;
                }

                if (!SIMPLE_PROPERTY_REGEX.test(key)) {
                    // true here means don't convert null to undefined
                    value = lib.nestedProperty(obj, key).get(true);
                }
                if (value !== undefined) break;
            }
        }

        if (value === undefined) {
            const { count, max, name } = opts;
            const fallbackValue = fallback === false ? match : fallback;
            if (count < max) {
                lib.warn(
                    [
                        `Variable '${key}' in ${name} could not be found!`,
                        'Please verify that the template is correct.',
                        `Using value: '${fallbackValue}'.`
                    ].join(' ')
                );
            }
            if (count === max) lib.warn(`Too many '${name}' warnings - additional warnings will be suppressed.`);
            opts.count++;

            return fallbackValue;
        }

        if (parsedOp === '*') value *= parsedNumber;
        if (parsedOp === '/') value /= parsedNumber;

        if (format) {
            var fmt;

View on GitHub (pinned to 1d090e0b5f)

Solutions

1. Verify the template key spelling matches a property present in the supplied object.
2. Provide the missing variable in the data object passed to the templater.
3. Pass a sensible `fallback` option so the substitution uses a known value instead of the raw placeholder.
4. If this comes from plotly internals (attribute text interpolation), check that the trace/layout attribute value you set matches the expected format.

Example fix

// before
templater('Hello ${name}!', {nmae: 'Ada'});
// after
templater('Hello ${name}!', {name: 'Ada'});

function validateTemplateVars(template, data) {
  const missing = [...template.matchAll(/\$\{(\w+)\}/g)]
    .map(m => m[1])
    .filter(k => data[k] === undefined);
  if (missing.length) throw new Error(`Missing template vars: ${missing}`);
}

function hasVar(data, key) { return typeof data === 'object' && data !== null && data[key] !== undefined; }

When it happens

Trigger: Calling the templating helper (src/lib/index.js templater) with a string containing a placeholder key that is absent from the provided data object, e.g. templater('Value: ${foo}', {bar: 1}).

Common situations: Typos in template keys, data objects with optional fields left undefined, renaming an object property without updating the template, or localized/custom attribute strings referencing removed variables.

Related errors

• Too many '${name}' warnings - additional warnings will be su

AI-assisted analysis of plotly/plotly.js@1d090e0b5f (2026-09-02). Data as JSON: /api/errors/d36197eb5618ec46. Report an issue: GitHub.