is any weightage marks for jee mains 2018?

Are you asking for chapter-wise weightage in JEE?

Below are the important topics weightage wise

Physics

Work, Energy and Power  Weightage: 5%
Electrostatics  Weightage: 6%
Current Electricity  Weightage: 7%
Wave Optics  Weightage: 5%
Ray Optics  Weightage: 6%
Centre of Mass, Momentum and Collision  Weightage: 5%
Rotational Dynamics  Weightage: 4%
Simple Harmonic Motion  Weightage: 5%
Fluid Mechanics  Weightage: 2  5%. Bernoullis principle can be easily twisted to ask some tricky questions.
Wave Motion and String Waves  Weightage: 5%
Magnetism  Weightage: 6%
Heat & Thermodynamics  Weightage: 6%. This is one topic that is very important for both Physics and Chemistry preparation in JEE.
Nuclear Physics  Weightage: 5%
Modern Physics  Weightage: 5%

Maths

3-D Geometry   Weightage: 5% Questions from this topic are generally straight forward so you can solve them easily by reading the questions properly.
Probability and Statistics   Weightage: 7%. I was weak in probability and paid the price for this. You should therefore try to familiarise yourself with various types of questions in Probability.
Vector Algebra   Weightage: 5%
Integration   Weightage: 8% (Definite + Indefinite integration)
Complex Numbers   Weightage: 5%
Parabola   Weightage: 3%
Trigonometric Ratios   Weightage: 3%

Chemistry

Atomic Structure  Weightage: 5%
Gaseous State  Weightage: 3%
Hydrocarbons  Weightage: 2%
Aldehydes and Ketones  Weightage: 5%
d & f Block Elements  Weightage: 5%
General Organic Chemistry  Weightage: 7%