let suppliedOptions; let options = suppliedOptions || { name: "デフォルト" } console.log(options); // { name: 'デフォルト' } suppliedOptions = null; options = suppliedOptions || { name: "デフォルト" } console.log(options); // { name: 'デフォルト' } suppliedOptions = {name : "xxx"}; options = suppliedOptions || { name: "デフォルト" } console.log(options); // { name: 'xxx' }