[Refactor] clean up quoteStyle code

Author: ljharb

index.js

@@ -69,10 +69,16 @@ var utilInspect = require('./util.inspect');
 var inspectCustom = utilInspect.custom;
 var inspectSymbol = isSymbol(inspectCustom) ? inspectCustom : null;
 
+var quotes = {
+    __proto__: null,
+    'double': '"',
+    single: "'"
+};
+
 module.exports = function inspect_(obj, options, depth, seen) {
     var opts = options || {};
 
-    if (has(opts, 'quoteStyle') && (opts.quoteStyle !== 'single' && opts.quoteStyle !== 'double')) {
+    if (has(opts, 'quoteStyle') && !has(quotes, opts.quoteStyle)) {
         throw new TypeError('option "quoteStyle" must be "single" or "double"');
     }
     if (
@@ -267,7 +273,8 @@ module.exports = function inspect_(obj, options, depth, seen) {
 };
 
 function wrapQuotes(s, defaultStyle, opts) {
-    var quoteChar = (opts.quoteStyle || defaultStyle) === 'double' ? '"' : "'";
+    var style = opts.quoteStyle || defaultStyle;
+    var quoteChar = quotes[style];
     return quoteChar + s + quoteChar;
 }