Create convert-json-string-to-object.ts

Author: kamyu104

TypeScript/convert-json-string-to-object.ts

@@ -0,0 +1,70 @@
+// Time:  O(n)
+// Space: O(h)
+
+// stack
+function jsonParse(str: string): any {
+    let stk = [];
+    let result = null;
+    let k = null;
+    for (let i = 0; i < str.length; i++) {
+        if (str[i] === "," || str[i] === ":") {
+            continue;
+        }
+        if (str[i] === '{' || str[i] === '[') {
+            let v = str[i] === '{' ? {} : [];
+            if (result !== null) {
+                if (k !== null) {
+                    result[k] = v;
+                    k = null;
+                } else {
+                    result.push(v);
+                }
+                stk.push(result);
+            }
+            result = v;
+        } else if (str[i] === '}' || str[i] === ']') {
+            if (stk.length !== 0) {
+                result = stk.pop();
+            }
+        } else {
+            let v;
+            if (str[i] === '-' || ('0' <= str[i] && str[i] <= '9')) {
+                let j = i;
+                while (i + 1 < str.length && 
+                       (str[i + 1] === '-' || ('0' <= str[i + 1] && str[i + 1] <= '9') || str[i + 1] === '.')) {
+                    i++;
+                }
+                v = Number(str.substring(j, i + 1));
+            } else if (str[i] === '"') {
+                let j = i + 1;
+                while (i + 1 < str.length && str[i + 1] !== '"') {
+                    i++;
+                }
+                v = str.substring(j, i + 1);
+                i++;
+            } else {
+                if (i + 3 < str.length && str.substring(i, i + 4) === "true") {
+                    v = true;
+                    i += 3;
+                } else if (i + 4 < str.length && str.substring(i, i + 5) === "false") {
+                    v = false;
+                    i += 4;
+                } else {
+                    v = null;
+                    i += 3;
+                }
+            }
+            if (result === null) {
+                result = v;
+            } else if (str[i + 1] === ":") {
+                k = v;
+            } else if (k !== null) {
+                result[k] = v;
+                k = null;
+            } else {
+                result.push(v);
+            }
+        }
+    }
+    return result;
+};