console.log('----1----')
console.log('12' + '34')//'1234'
console.log('12' + 34 )//'1234'
console.log(12 + '34')//'1234'
console.log(12 + 34 )//46
console.log('----2----')
console.log(+'12' + '34')//'1234'
console.log(+'12' + 34 )//46
console.log(+12 + '34')//'1234'
console.log(+12 + 34 )//46
console.log('----3----')
console.log(-'12' + '34')//'-1234'
console.log(-'12' + 34)//22
console.log(-12 + '34')//'-1234'
console.log(-12 + 34)//22
console.log('----4----')
console.log('12' - '34')//-22
console.log('12' - 34)//-22
console.log(12 - '34')//-22
console.log(12 - 34)//-22
console.log('----5----')
console.log(+'12' - '34')//-22
console.log(+'12' - 34)//-22
console.log(+12 - '34')//-22
console.log(+12 - 34)//-22
console.log('----6----')
console.log(-'12' - '34')//-22
console.log(-'12' - 34)//-22
console.log(-12 - '34')//-22
console.log(-12 - 34)//-22