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In most cases, the value of <em>this </em>is determined by how a function is called. It can’t be set by assignment during execution, and it may be different each time the function is called. You can change <em>this </em>context through <em>.call()</em>, <em>.apply()</em> and <em>.bind().</em> Value of <em>this</em> is equal to the value of the object which invokes the function. <em>this</em> is not assigned a value until an object invokes the function where <em>this</em> is defined.