99 bottles of beer as short as possible in ECMAScript 6 - currently 142 characters

99bottles.js

x=""
b=r=>`${c||"No more"} bottle${c-1?"s":""} of beer${r&&c--||" on the wall"}
`
for(c=99;c;)x+=b()+b(1)+`Take one down, pass it around
`+b()

Tested in an ES6 VM over at http://benvie.github.io/continuum/

No need for var?

Indeed! Good remark! down to 167!

q=" of beer",o=q+" on the wall",b=c=>`${c?c:"No more"} bottle${c-1?"s":""}`
for(i=99;i>0;){x+=`${b(i)+o}
${b(i)+q}
Take one down, pass it around
${b(--i)+o}`}
x

Down to 155.

And down to 164... maybe I might be able to fit it in a tweet? 😃

Hmm, one small mistake.

q=" of beer",o=q+" on the wall",b=c=>`${c?c:"No more"} bottle${c-1?"s":""}`,x=''
for(i=99;i>0;)x+=`${b(i)+o}
${b(i)+q}
Take one down, pass it around
${b(--i)+o}
`
x

EDIT: fixed it here, no overall gain.

it doesn't seem to work when I try in http://benvie.github.io/continuum/ ?

If fixed my version, but it's not better then yours with the mistakes fixed. I think a different approach is needed to shave more of...

160 chars

159:

b=(c,r)=>`${c||"No more"} bottle${c-1?"s":""} of beer${r?"":" on the wall"}`,v=c=>!c||`${b(c)}
${b(c,1)}
Take one down, pass it around
${b(--c)}
${v(c)}`
v(99)

154:

x=""
for(c=99;c;){
b=r=>`${c||"No more"} bottle${c-1?"s":""} of beer${r?c--||"":" on the wall"}`
x+=b()+`
${b(c)}
Take one down, pass it around
${b()}
`}x

Do you even need to declare x=""?

@abdullin yeah, ReferenceError

152:

b=r=>`${c||"No more"} bottle${c-1?"s":""} of beer${r?c--||"":" on the wall"}`,x=""
for(c=99;c;)x+=b()+`
${b(1)}
Take one down, pass it around
${b()}
`
x

150 (don't need the x at the end to print)

b=r=>`${c||"No more"} bottle${c-1?"s":""} of beer${r?c--||"":" on the wall"}`,x=""
for(c=99;c;)x+=b()+`
${b(1)}
Take one down, pass it around
${b()}
`

148 (forgot an easy one)

b=r=>`${c|"No more"} bottle${c-1?"s":""} of beer${r?c--|"":" on the wall"}`,x=""
for(c=99;c;)x+=b()+`
${b(1)}
Take one down, pass it around
${b()}
`

147 - almost tweetable!

x=""
for(c=99;c;)
b=r=>`${c||"No more"} bottle${c-1?"s":""} of beer${r?c--||"":" on the wall"}
`,x+=b()+b(1)+`Take one down, pass it around
`+b()
x

@ToJans don't forget to change || by |

142 chars!

x=""
b=r=>`${c|"No more"} bottle${c-1?"s":""} of beer${r?c--|"":" on the wall"}
`
for(c=99;c;)x+=b()+b(1)+`Take one down, pass it around
`+b()

You can't change || by |, or the last sentence is wrong; so back to 143 chars...