After the yarn start command, the terminal give me a lot of warning, this is only a part of it:
WARNING in bundle.js from UglifyJs
Condition always false [bundle.js:96,4]
Dropping unreachable code [bundle.js:97,2]
Condition always false [bundle.js:155,4]
Dropping unreachable code [bundle.js:156,2]
Condition always false [bundle.js:447,13]
Condition always true [bundle.js:447,5]
Condition always false [bundle.js:506,37]
Condition always false [bundle.js:516,25]
Side effects in initialization of unused variable invariant [bundle.js:362,4]
Condition always false [bundle.js:604,4]
Dropping unreachable code [bundle.js:604,11]
Declarations in unreachable code! [bundle.js:605,2]
Condition always false [bundle.js:693,4]
Dropping unreachable code [bundle.js:693,11]
Declarations in unreachable code! [bundle.js:694,2]
Condition always false [bundle.js:736,67]
Condition always false [bundle.js:817,39]
Condition always false [bundle.js:919,41]
Condition always false [bundle.js:926,29]
Condition always false [bundle.js:931,26]
Condition always false [bundle.js:932,65]
Condition always false [bundle.js:933,67]
Side effects in initialization of unused variable invariant [bundle.js:726,4]
Condition always false [bundle.js:1057,6]
Dropping unreachable code [bundle.js:1059,4]
Condition always false [bundle.js:1073,8]
Dropping unreachable code [bundle.js:1074,6]
Condition always false [bundle.js:1257,5]
Dropping side-effect-free statement [bundle.js:1257,5]
Condition always false [bundle.js:1158,10]
Dropping unreachable code [bundle.js:1159,8]
Condition always false [bundle.js:1167,8]
Dropping unreachable code [bundle.js:1168,6]
Condition always false [bundle.js:1177,4]
Dropping unreachable code [bundle.js:1178,2]
Side effects in initialization of unused variable warning [bundle.js:1012,4]
Condition always false [bundle.js:1336,34]
Side effects in initialization of unused variable invariant [bundle.js:1281,4]
Condition always false [bundle.js:1403,4]
Dropping unreachable code [bundle.js:1404,2]
Condition always false [bundle.js:1478,4]
Dropping unreachable code [bundle.js:1478,11]
Declarations in unreachable code! [bundle.js:1479,2]
Condition always false [bundle.js:1493,4]
Dropping unreachable code [bundle.js:1493,11]
Declarations in unreachable code! [bundle.js:1494,2]
Condition always false [bundle.js:1544,4]
Dropping unreachable code [bundle.js:1544,11]
Declarations in unreachable code! [bundle.js:1545,2]
Declarations in unreachable code! [bundle.js:1568,2]
Condition always false [bundle.js:1619,6]
Dropping unreachable code [bundle.js:1620,4]
Declarations in unreachable code! [bundle.js:1621,6]
Condition always false [bundle.js:1631,6]
Dropping unreachable code [bundle.js:1632,4]
Declarations in unreachable code! [bundle.js:1633,6]
Condition always false [bundle.js:1646,7]
Dropping side-effect-free statement [bundle.js:1646,7]
Condition always false [bundle.js:1660,7]
Dropping side-effect-free statement [bundle.js:1660,7]
Condition always false [bundle.js:1705,6]
Dropping unreachable code [bundle.js:1710,4]
Condition always false [bundle.js:1795,8]
Dropping unreachable code [bundle.js:1796,6]
Condition always false [bundle.js:1812,6]
Dropping unreachable code [bundle.js:1813,4]
Declarations in unreachable code! [bundle.js:1815,8]
Side effects in initialization of unused variable self [bundle.js:1863,6]
Side effects in initialization of unused variable source [bundle.js:1867,6]
Side effects in initialization of unused variable warning [bundle.js:1603,4]
Side effects in initialization of unused variable canDefineProperty [bundle.js:1604,4]
Condition always false [bundle.js:2005,59]
Condition always false [bundle.js:2022,118]
Condition always false [bundle.js:2024,10]
Dropping unreachable code [bundle.js:2025,8]
Condition always false [bundle.js:2031,12]
Dropping unreachable code [bundle.js:2032,10]
Condition always false [bundle.js:2116,28]
Side effects in initialization of unused variable invariant [bundle.js:1947,4]
Condition always false [bundle.js:2186,8]
Dropping unreachable code [bundle.js:2187,6]
Condition always false [bundle.js:2195,8]
Dropping unreachable code [bundle.js:2196,6]
Condition always false [bundle.js:2218,8]
Dropping unreachable code [bundle.js:2219,6]
Condition always false [bundle.js:2225,8]
Dropping unreachable code [bundle.js:2226,6]
Condition always false [bundle.js:2258,8]
Dropping unreachable code [bundle.js:2259,6]
Condition always false [bundle.js:2276,8]
Dropping unreachable code [bundle.js:2277,6]
Condition always false [bundle.js:2294,7]
Dropping side-effect-free statement [bundle.js:2294,7]
Condition always false [bundle.js:2297,8]
Dropping unreachable code [bundle.js:2298,6]
Condition always false [bundle.js:2303,8]
Dropping unreachable code [bundle.js:2304,6]
Side effects in initialization of unused variable ReactInstrumentation [bundle.js:2160,4]
Side effects in initialization of unused variable warning [bundle.js:2162,4]
Condition always false [bundle.js:2522,6]
Dropping unreachable code [bundle.js:2523,4]
Side effects in initialization of unused variable warning [bundle.js:2502,4]
Condition always false [bundle.js:2755,41]
Condition always false [bundle.js:2879,20]
Side effects in initialization of unused variable invariant [bundle.js:2644,4]
Side effects in initialization of unused variable addLeadingSlash [bundle.js:3021,4]
Side effects in initialization of unused variable stripLeadingSlash [bundle.js:3025,4]
Side effects in initialization of unused variable stripPrefix [bundle.js:3029,4]
Side effects in initialization of unused variable stripTrailingSlash [bundle.js:3033,4]
Side effects in initialization of unused variable parsePath [bundle.js:3037,4]
Side effects in initialization of unused variable createPath [bundle.js:3063,4]
Condition always false [bundle.js:3097,4]
Dropping unreachable code [bundle.js:3098,2]
Condition always false [bundle.js:3239,32]
Condition always false [bundle.js:3303,31]
Side effects in initialization of unused variable invariant [bundle.js:3123,4]
Condition always false [bundle.js:4000,6]
Dropping unreachable code [bundle.js:4001,4]
Condition always false [bundle.js:4075,27]
Condition always false [bundle.js:4079,35]
Condition always false [bundle.js:4083,85]
Condition always false [bundle.js:4097,78]
Condition always false [bundle.js:4125,69]
Condition always false [bundle.js:4129,6]
Dropping unreachable code [bundle.js:4129,13]
Declarations in unreachable code! [bundle.js:4130,4]
Condition always false [bundle.js:4171,30]
Condition always false [bundle.js:4184,26]
Condition always false [bundle.js:4208,40]
Condition always false [bundle.js:4275,8]