I'm a web developer using python and javascript.
I move here and there to study, develop and have a meeting.
My favorite OS is linux, Ubuntu 16.04 LTS.

I have three laptops and let me introduce them.
I'll give you what to consider buying laptop as a web developer.

Macbook Pro Retina 13inch late 2013

spec : CORE i5 2.4GHz, RAM 4GB, SSD 128GB

I planned to buy Macbook air, for my laptop were too heavy, more than 2kg.
But I found Retina beautiful, I bought the cheapest MBP Retina 13".

Fits : Great for Eye, Hardy case, Great Touch.
Falls : little bit heavy, not cheap, upgrade IMPOSSIBLE: RAM, CPU soldered

I have two FHD monitors at home,
and I connected the two with HDMI and Thunderbolt(mini DP)
It is very nice environment for developing.
One is for coding, second for browser, the last one for reference docs.
In this case you may need keyboard and mouse.

I like the program Retina Display Mode https://github.com/avibrazil/RDM which makes external monitors looks like Retina display. (Screenshot is from the avibrazil github site)

Until last year, MBP was my favorite.
I found a little bit heavy is quite good for using on my both laps, which means REAL LAP TOP.
Lighter one was unstable on my laps, easily slip down.

Lenovo Y50

spec : CORE i7 2.8GHz, RAM 16GB, SSD 256GB, 15" FHD display

I got interest in machine learning and OpenCV. I bought this guy.

Fits : cheap, nVidia GTX 960 with 4GB RAM
Falls : bad display(TN pannel), bad keyboard, a little bit heavy (over 2kg)

For the bad display, I have to use external LCD.
Portability was limited and it is used as desktop.

Later I replaced it with IPS.
Most of laptop LCD pannel are replaceable.
If you feel uneasy for the bad TN pannel, you can find IPS pannel with same connector.

The keyboard has numeric keypad on the right, I think this is bad design for laptop.
I have to reach laptop a little bit left side, and this makes REAL LAP TOP impossible.
Some people like numeric, but NEVER for me.

LG Gram 14inch

spec : Pentium 2.1Ghz with Intel HD 510, RAM 8GB, SSD 256GB

Fits : Good IPS display, keyboard without numeric, very light (only 980g)
Falls : low CPU, single RAM slot allows only 8GB max.

I have got this guy at the end of last year.
I need a Window computer for personal use not an expensive, easy to carry.
First it has 4GB RAM, SSD 128GB and Window OS,
Booting time is only 3 secs. I think Intel did great work with MS.

At this time, MBP make short of memory running WEB server, Python IDE and Browser.
I upgraded Gram with 8GB, 256GB and installed linux Ubuntu 16.04.
Gram and Linux match perfect.

Now this one is my favorite.
I found CPU power was not critical for web developer.
I'm doing FE and BE at the same time.
It sometimes run short of memory and use swap disk, but this doesn't down the perf.

Keyboard layout is good for me, it doesn't have numeric on the right.
Good enough touch, I can uses this without mouse.