如何从用户位置连接到目的地?

I want to draw a line from current user location to destination using google map

I have this hardcoded value, how to make it dynamic.

<iframe src="https://www.google.com/maps/embed?pb=!1m28!1m12!1m3!1d62184.85911505553!2d77.54398420640405!3d13.064056093502584!2m3!1f0!2f0!3f0!3m2!1i1024!2i768!4f13.1!4m13!3e6!4m5!1s0x3bae229f7a8debe1%3A0x4d80f1d259c7e7ac!2sVidyaranyapura%2C+Bengaluru%2C+Karnataka!3m2!1d13.0857908!2d77.55609799999999!4m5!1s0x3bae1782c59f1f99%3A0x536d89574c4f1216!2sNagavara%2C+Bengaluru%2C+Karnataka!3m2!1d13.0422567!2d77.6135523!5e0!3m2!1sen!2sin!4v1486457746829" width="600" height="450" frameborder="0" style="border:0" allowfullscreen></iframe>

my question: my destination will be fixed like var dest = "yelhanka"; i want to draw line from current user location to my destination dynamically(i,e yelhanka)

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