The spec also uses language values internally, for example, an internal data type might contain a field whose possible values are true and false. They are all language values, values of language types which the spec also defines. The spec uses values such as undefined, true, and false, which we already know from JavaScript. Let’s start with something that looks familiar. Let’s find out! Language types and specification types # This abstract operation performs the following steps:īut what’s an “abstract operation”? What are the things inside ]? Why is there a ? in front of a function? What do the asserts mean? The operation is called with arguments O and P where O is the object and P is the property key. The abstract operation HasOwnProperty is used to determine whether an object has an own property with the specified property key.
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