Create valid_number.js

Author: Jaskaran Singh

valid_number.js

@@ -0,0 +1,104 @@
+/**
+ * @param {string} s
+ * @return {boolean}
+ */
+let hasADot = 0;
+let hasAnE = 0;
+
+var isNumber = function(s) {
+    hasADot = 0;
+    hasAnE = 0;
+    s = s.trim();
+    return validateForFirstCharacter(s);
+};
+
+let validateForFirstCharacter = (s) => {
+    if(validateFirstCharacter(s[0])) {
+        if(!isNaN(s[0]))
+            return validateForNumber(s, 0);
+        else if(s[0] === "+" || s[0] === "-")
+            return validateForSign(s, 0);
+        else if(s[0] === ".")
+            return validateForDot(s, 0);
+        else
+            return false;
+    } else
+        return false;
+}
+
+
+let validateFirstCharacter = (fc) => {
+    return (!isNaN(fc) || fc === "+" || fc === "-" || fc === "." || fc === " ");
+}
+
+let validateForNumber = (currentString, currentIndex) => {
+    let nextCharacter = currentString[currentIndex + 1];
+    
+    if(nextCharacter === undefined)
+        return true;
+    else if(nextCharacter === " ")
+        return false;
+    else if(nextCharacter === ".")
+        return validateForDot(currentString, currentIndex + 1);
+    else if(nextCharacter === "e")
+        return validateForE(currentString, currentIndex + 1);
+    else if(!isNaN(nextCharacter))
+        return validateForNumber(currentString, currentIndex + 1);
+    else
+        return false;
+}
+
+let validateForSign = (currentString, currentIndex) => {
+    let nextCharacter = currentString[currentIndex + 1];
+    
+    if(nextCharacter === "." && !isNaN(currentString[currentIndex + 2]))
+        return validateForDot(currentString, currentIndex + 1);
+    else if(!isNaN(nextCharacter) && nextCharacter !== " ")
+        return validateForNumber(currentString, currentIndex + 1);
+    else
+        return false;
+}
+
+let validateForDot = (currentString, currentIndex) => {
+    let nextCharacter = currentString[currentIndex + 1];
+    
+    if(hasADot)
+        return false;
+    
+    hasADot = 1;
+    
+    if(hasAnE)
+        return false;
+    
+    if(nextCharacter === undefined) {
+        if(currentIndex === 0)
+            return false;
+        else
+            return true;
+    } else if(!isNaN(nextCharacter) && nextCharacter !== " ")
+        return validateForNumber(currentString, currentIndex + 1);
+    else if(nextCharacter === "e") {
+        if(currentString[currentIndex - 1] === undefined)
+            return false;
+        
+        return validateForE(currentString, currentIndex + 1);   
+    }
+    else
+        return false;
+}
+
+let validateForE = (currentString, currentIndex) => {
+    let nextCharacter = currentString[currentIndex + 1];
+
+    if(hasAnE)
+            return false;
+    
+    hasAnE = 1;
+
+    if(nextCharacter === "+" || nextCharacter === "-") {
+        return validateForSign(currentString, currentIndex + 1);
+    } else if(!isNaN(nextCharacter)) {
+        return validateForNumber(currentString, currentIndex + 1);
+    } else
+        return false;
+}