Custom ES Lint rule to avoid and fix two or more spaces in string or className.

no-multi-space-in-strings.js

export default {
  meta: {
    type: 'problem',
    docs: {
      description: 'Disallow multiple consecutive spaces in string literals',
      category: 'Possible Errors',
      recommended: true,
    },
    fixable: 'code',
    schema: [],
    messages: {
      noMultiSpace: 'Avoid using multiple consecutive spaces in string literals.',
    },
  },

  create(context) {
    return {
      Literal(node) {
        if (typeof node.value !== 'string') return;
        if (/\s{2,}/.test(node.value)) {
          context.report({
            node,
            messageId: 'noMultiSpace',
            fix(fixer) {
              const fixed = node.value.replace(/\s{2,}/g, ' ');
              return fixer.replaceText(node, JSON.stringify(fixed));
            },
          });
        }
      },
      TemplateElement(node) {
        if (/\s{2,}/.test(node.value.raw)) {
          context.report({
            node,
            messageId: 'noMultiSpace',
            fix(fixer) {
              const fixed = node.value.raw.replace(/\s{2,}/g, ' ');
              const rawText = '`' + fixed + '`';
              return fixer.replaceText(node, rawText);
            },
          });
        }
      },
    };
  },
};