run start:dev failes Unexpected identifier in concurrently - node.js

Question

I'm rather new to the nodejs world and having trouble with some basics ,
when I do npm install it shows a few warn messages but complete it .
when I do npm build it works fine
but when I do run start:dev it crashes with this error message :
concurrently\bin\concurrently.js:140
let lastColor;
^^^^^^^^^
SyntaxError: Unexpected identifier
at exports.runInThisContext (vm.js:73:16)
at Module._compile (module.js:443:25)
at Object.Module._extensions..js (module.js:478:10)
at Module.load (module.js:355:32)
at Function.Module._load (module.js:310:12)
at Function.Module.runMain (module.js:501:10)
at startup (node.js:129:16)
at node.js:814:3
npm ERR! Windows_NT 6.3.9600
npm ERR! argv "C:\\Program Files (x86)\\nodejs\\\\node.exe" "C:\\Program Files (x86)\\nodejs\\node_modules\\npm\\bin\\npm-cli.js" "run" "start:dev"
npm ERR! node v0.12.2
npm ERR! npm v2.7.4
npm ERR! code ELIFECYCLE
npm ERR! izi-backend#0.0.1 start:dev: `concurrently --handle-input "wait-on dist/main.js && nodemon" "tsc -w -p tsconfig.build.json" `
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the izi-backend#0.0.1 start:dev script 'concurrently --handle-input "wait-on dist/main.js && nodemon" "tsc -w -p tsconfig.build.json" '.
npm ERR! This is most likely a problem with the izi-backend package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR! concurrently --handle-input "wait-on dist/main.js && nodemon" "tsc -w -p tsconfig.build.json"
npm ERR! You can get their info via:
npm ERR! npm owner ls izi-backend
npm ERR! There is likely additional logging output above.
npm ERR! Please include the following file with any support request:
npm ERR! C:\dev\iziMobile\izi-server\npm-debug.log
where npm run start:dev is defined as :
"start:dev": "concurrently --handle-input \"wait-on dist/main.js && nodemon\" \"tsc -w -p tsconfig.build.json\" "
also printing out npm-debug.log:
0 info it worked if it ends with ok
1 verbose cli [ 'C:\Program Files (x86)\nodejs\\node.exe',
1 verbose cli 'C:\Program Files (x86)\nodejs\node_modules\npm\bin\npm-cli.js',
1 verbose cli 'run',
1 verbose cli 'start:dev' ]
2 info using npm#2.7.4
3 info using node#v0.12.2
4 verbose node symlink C:\Program Files (x86)\nodejs\node.exe
5 verbose run-script [ 'prestart:dev', 'start:dev', 'poststart:dev' ]
6 info prestart:dev izi-backend#0.0.1
7 info start:dev izi-backend#0.0.1
8 verbose unsafe-perm in lifecycle true
9 info izi-backend#0.0.1 Failed to exec start:dev script
10 verbose stack Error: izi-backend#0.0.1 start:dev: concurrently --handle-input "wait-on dist/main.js && nodemon" "tsc -w -p tsconfig.build.json"
10 verbose stack Exit status 1
10 verbose stack at EventEmitter. (C:\Program Files (x86)\nodejs\node_modules\npm\lib\utils\lifecycle.js:213:16)
10 verbose stack at EventEmitter.emit (events.js:110:17)
10 verbose stack at ChildProcess. (C:\Program Files (x86)\nodejs\node_modules\npm\lib\utils\spawn.js:14:12)
10 verbose stack at ChildProcess.emit (events.js:110:17)
10 verbose stack at maybeClose (child_process.js:1015:16)
10 verbose stack at Process.ChildProcess._handle.onexit (child_process.js:1087:5)
11 verbose pkgid izi-backend#0.0.1
12 verbose cwd C:\dev\iziMobile\izi-server
13 error Windows_NT 6.3.9600
14 error argv "C:\Program Files (x86)\nodejs\\node.exe" "C:\Program Files (x86)\nodejs\node_modules\npm\bin\npm-cli.js" "run" "start:dev"
15 error node v0.12.2
16 error npm v2.7.4
17 error code ELIFECYCLE
18 error izi-backend#0.0.1 start:dev: concurrently --handle-input "wait-on dist/main.js && nodemon" "tsc -w -p tsconfig.build.json"
18 error Exit status 1
19 error Failed at the izi-backend#0.0.1 start:dev script 'concurrently --handle-input "wait-on dist/main.js && nodemon" "tsc -w -p tsconfig.build.json" '.
19 error This is most likely a problem with the izi-backend package,
19 error not with npm itself.
19 error Tell the author that this fails on your system:
19 error concurrently --handle-input "wait-on dist/main.js && nodemon" "tsc -w -p tsconfig.build.json"
19 error You can get their info via:
19 error npm owner ls izi-backend
19 error There is likely additional logging output above.
20 verbose exit [ 1, true ]<
Concurrently is a package I take in packages.json so I doubt there is really an error there...
Am I missing anything ?
Any help will do at this point

Answer 1

Node v0.12.2 does not support the let declarations.
See here for the full version support matrix.

Answer 2

You are using node version v0.12.2. let syntax is not supported.
From node.green you can see that let is supported from Node v6.4.x