axe-core/lib/checks/mobile/meta-viewport-scale-evaluate.js

Accessibility engine for automated Web UI testing

function metaViewportScaleEvaluate(node, options, virtualNode) {
  const { scaleMinimum = 2, lowerBound = false } = options || {};

  const content = virtualNode.attr('content') || '';
  if (!content) {
    return true;
  }

  const result = content.split(/[;,]/).reduce((out, item) => {
    const contentValue = item.trim();
    if (!contentValue) {
      return out;
    }

    const [key, value] = contentValue.split('=');
    if (!key || !value) {
      return out;
    }
    const curatedKey = key.toLowerCase().trim();
    let curatedValue = value.toLowerCase().trim();

    // convert `yes` to `1`
    if (curatedKey === 'maximum-scale' && curatedValue === 'yes') {
      curatedValue = 1;
    }
    // when negative ignore key
    if (curatedKey === 'maximum-scale' && parseFloat(curatedValue) < 0) {
      return out;
    }

    out[curatedKey] = curatedValue;
    return out;
  }, {});

  if (
    lowerBound &&
    result['maximum-scale'] &&
    parseFloat(result['maximum-scale']) < lowerBound
  ) {
    return true;
  }

  if (!lowerBound && result['user-scalable'] === 'no') {
    this.data('user-scalable=no');
    return false;
  }

  const userScalableAsFloat = parseFloat(result['user-scalable']);
  if (
    !lowerBound &&
    result['user-scalable'] &&
    (userScalableAsFloat || userScalableAsFloat === 0) &&
    userScalableAsFloat > -1 &&
    userScalableAsFloat < 1
  ) {
    this.data('user-scalable');
    return false;
  }

  if (
    result['maximum-scale'] &&
    parseFloat(result['maximum-scale']) < scaleMinimum
  ) {
    this.data('maximum-scale');
    return false;
  }

  return true;
}

export default metaViewportScaleEvaluate;