code: function handleWarnings(warnings) {
    clearOutdatedErrors();
    destroyErrorOverlay();
  
    var isHotUpdate = !isFirstCompilation;
    isFirstCompilation = false;
    hasCompileErrors = false;
  
    function printWarnings() {
      // Print warnings to the console.
      for (var i = 0; i < warnings.length; i++) {
        console.warn(stripAnsi(warnings[i]));
      }
    }
  
    // Attempt to apply hot updates or reload.
    if (isHotUpdate) {
      tryApplyUpdates(function onSuccessfulHotUpdate() {
        // Only print warnings if we aren't refreshing the page.
        // Otherwise they'll disappear right away anyway.
        printWarnings();
      });
    } else {
      // Print initial warnings immediately.
      printWarnings();
    }
  }
docs: Compilation with warnings (e.g. ESLint).