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75 lines
2.9 KiB
75 lines
2.9 KiB
=proto
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int duk_del_prop(duk_context *ctx, int obj_index);
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=stack
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[ ... obj! ... key! ] -> [ ... obj! ... ]
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=summary
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<p>Delete the property <code>key</code> of a value at <code>obj_index</code>.
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<code>key</code> is removed from the stack. Return code and error throwing
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behavior:</p>
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<ul>
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<li>If property exists and is configurable (deletable), deletes the
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property and returns non-zero.</li>
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<li>If property exists but is not configurable, throws an error if current
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function is strict, returns 0 otherwise.</li>
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<li>If property does not exist, returns non-zero (<i>not</i> 0).</li>
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<li>If the value at <code>obj_index</code> is not
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<a href="http://www.ecma-international.org/ecma-262/5.1/#sec-9.10">object coercible</a>,
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throws an error.</li>
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<li>If <code>obj_index</code> is invalid, throws an error.</li>
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</ul>
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<p>The property deletion is equivalent to the Ecmascript expression:</p>
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<pre class="ecmascript-code">
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delete obj[key]
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</pre>
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<p>For semantics, see
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<a href="http://www.ecma-international.org/ecma-262/5.1/#sec-11.2.1">Property Accessors</a>,
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<a href="http://www.ecma-international.org/ecma-262/5.1/#sec-11.4.1">The delete operator</a>
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and <a href="http://www.ecma-international.org/ecma-262/5.1/#sec-8.12.7">[[Delete]] (P, Throw)</a>.
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The return value and error throwing behavior mirrors the Ecmascript
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<code>delete</code> operator behavior.
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Both the target value and the <code>key</code> are coerced:</p>
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<ul>
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<li>The target value is automatically coerced to an object. However, this
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object is a temporary one, so deleting its properties is not very useful.</li>
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<li>The <code>key</code> argument is internally coerced to a string. There is
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an internal fast path for arrays and numeric indices which avoids an
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explicit string coercion, so use a numeric <code>key</code> when applicable.</p>
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</ul>
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<div class="note">
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This API call returns non-zero when the target property does not exist.
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This is not very intuitive, but follows Ecmascript semantics:
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<code>delete obj.nonexistent</code> also evaluates to <code>true</code>.
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</div>
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<div class="note">
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At the moment all Duktape/C functions are strict. When called from a
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Duktape/C function, this API call thus either returns non-zero or throws
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an error. However, if called outside a Duktape/C function (when the
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context has an empty call stack) the API call executes in non-strict mode,
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i.e. returns 0 when trying to delete a non-configurable property.
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</div>
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<p>If the key is a fixed string you can avoid one API call and use the
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<code><a href="#duk_del_prop_string">duk_del_prop_string()</a></code> variant.
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Similarly, if the key is an array index, you can use the
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<code><a href="#duk_del_prop_index">duk_del_prop_index()</a></code> variant.</p>
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=example
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int rc;
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duk_push_string(ctx, "myProperty");
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rc = duk_del_prop(ctx, -3);
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printf("delete obj.myProperty -> rc=%d\n", rc);
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=tags
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property
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=seealso
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duk_del_prop_string
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duk_del_prop_index
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