study-notes/subjects/webpack/06-其他常用工程化工具/35_rollup的其他文件/dist/sq.umd.js
/**
   * Ensure a function is called only once.
   */
Ensure a function is called only once.
Ensure a function is called only once .
function once(fn) {
    var called = false;
    return function () {
      if (!called) {
        called = true;
        fn.apply(this, arguments);
      }
    };
  }
function once ( fn ) { var called = false ; return function ( ) { if ( ! called ) { called = true ; fn . apply ( this , arguments ) ; } } ; }
Ensure a function is called only once.
Ensure a function is called only once .