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This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.
Determine whether script is executing assignment operation.
JSBool JS_IsAssigning(JSContext *cx);
true if a script is executing and its current bytecode is a set (assignment) operation, even if there are native (no script) stack frames between the script and the caller to