javascript - Why use this obj.method.call(obj, arg) and not obj.method(arg)? -

i see pattern sometimes...

obj.method.call(obj, arg)   

and don't understand why different from...

obj.method(arg)   

why use first pattern?

my goodness, seems have generated lot of discussion :)

just clarify, asking case when object method on same first argument of call() (or maybe @felixkling put better: when owner same receiver). i'm not asking obj.method.call(obj2, arg).

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as mentioned below, case when function bound fails differentiate 2 methods.

o2={p2:3}; o={p1:(function(){return this.p2}).bind(o2), p2:2}; o.p1() === o.p1.call(o) // true   

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edit

i guess source of idiom pattern used rebind object's methods...

obj.method.apply(obj, arguments) 

why use obj.method.call(obj, arg) , not obj.method(arg)?

there no practical reason this.

in both cases this refer obj, assuming function not bound different value (in case this bound value anyway).