思路
考慮完全所有情況
1.只能出現(xiàn)數(shù)字爷怀、符號位阻肩、小數(shù)點、指數(shù)位
2.小數(shù)點运授，指數(shù)符號只能出現(xiàn)一次烤惊、且不能出現(xiàn)在開頭結(jié)尾
3.指數(shù)位出現(xiàn)后乔煞，小數(shù)點不允許在出現(xiàn)
4.符號位只能出現(xiàn)在開頭和指數(shù)位后面
function isNumeric(s) {
if (s == undefined) {
return false;
}
let hasPoint = false;
let hasExp = false;
for (let i = 0; i < s.length; i++) {
const target = s[i];
if (target >= 0 && target <= 9) {
continue;
} else if (target === 'e' || target === 'E') {
if (hasExp || i === 0 || i === s.length - 1) {
return false;
} else {
hasExp = true;
continue;
}
} else if (target === '.') {
if (hasPoint || hasExp || i === 0 || i === s.length - 1) {
return false;
} else {
hasPoint = true;
continue;
}
} else if (target === '-' || target === '+') {
if (i === 0 || s[i - 1] === 'e' || s[i - 1] === 'E') {
continue;
} else {
return false;
}
} else {
return false;
}
}
return true;
}
