node_modules/stylelint/lib/utils/isStandardSyntaxValue.js

/* @flow */
"use strict";

const hasInterpolation = require("../utils/hasInterpolation");

/**
 * Check whether a value is standard
 */
module.exports = function(value /*: string*/) /*: boolean*/ {
  let normalizedValue = value;

  // Ignore operators before variables (example -$variable)
  if (/^[-+*/]/.test(value[0])) {
    normalizedValue = normalizedValue.slice(1);
  }

  // SCSS variable
  if (normalizedValue[0] === "$") {
    return false;
  }

  // Less variable
  if (normalizedValue[0] === "@") {
    return false;
  }

  // SCSS or Less interpolation
  if (hasInterpolation(normalizedValue)) {
    return false;
  }

  return true;
};