Function getReplacedValueOrUndefined

test/babel.js:50432–50453

(holder, key, isTopLevel)

	        throw new Error('Replacer must be a function or an array');
	    }
	    var getReplacedValueOrUndefined = function getReplacedValueOrUndefined(holder, key, isTopLevel) {
	        var value = holder[key];

	        // Replace the value with its toJSON value first, if possible
	        if (value && value.toJSON && typeof value.toJSON === "function") {
	            value = value.toJSON();
	        }

	        // If the user-supplied replacer if a function, call it. If it's an array, check objects' string keys for
	        // presence in the array (removing the key/value pair from the resulting JSON if the key is missing).
	        if (typeof replacer === "function") {
	            return replacer.call(holder, key, value);
	        } else if (replacer) {
	            if (isTopLevel || isArray(holder) || replacer.indexOf(key) >= 0) {
	                return value;
	            } else {
	                return undefined;
	            }
	        } else {
	            return value;
	        }
	    };

	    function isWordChar(c) {
	        return c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c >= '0' && c <= '9' || c === '_' || c === '$';