use execute method

src/database.js

@@ -0,0 +1,101 @@
+import sqliteParser from 'sqlite-parser'
+const worker = new Worker('js/worker.sql-wasm.js')
+
+export default {
+  loadDb (file) {
+    return new Promise((resolve, reject) => {
+      const f = file
+      const r = new FileReader()
+      r.onload = () => {
+        // on 'action: open' completed
+        worker.onmessage = () => {
+          const getSchemaSql = `
+            SELECT name, sql
+            FROM sqlite_master
+            WHERE type='table' AND name NOT LIKE 'sqlite_%';`
+
+          this.execute(getSchemaSql)
+            .then(result => {
+              // Parse DDL statements to get column names and types
+              const parsedSchema = []
+              result.values.forEach(item => {
+                parsedSchema.push({
+                  name: item[0],
+                  columns: getColumns(item[1])
+                })
+              })
+
+              // Return db name and schema
+              resolve({
+                dbName: file.name,
+                schema: parsedSchema
+              })
+            })
+        }
+
+        try {
+          worker.postMessage({ action: 'open', buffer: r.result }, [r.result])
+        } catch (exception) {
+          worker.postMessage({ action: 'open', buffer: r.result })
+        }
+      }
+      r.readAsArrayBuffer(f)
+    })
+  },
+  execute (commands) {
+    return new Promise((resolve, reject) => {
+      worker.onmessage = (event) => {
+        if (event.data.error) {
+          reject(event.data.error)
+        }
+        // if it was more than one select - take only the first one
+        resolve(event.data.results[0])
+      }
+      worker.postMessage({ action: 'exec', sql: commands })
+    })
+  }
+}
+
+function getAst (sql) {
+  // There is a bug is sqlite-parser
+  // It throws an error if tokenizer has an arguments:
+  // https://github.com/codeschool/sqlite-parser/issues/59
+  const fixedSql = sql
+    .replace(/(?<=tokenize=.+)"tokenchars=.+"/, '')
+    .replace(/(?<=tokenize=.+)"remove_diacritics=.+"/, '')
+    .replace(/(?<=tokenize=.+)"separators=.+"/, '')
+    .replace(/tokenize=.+(?=(,|\)))/, 'tokenize=unicode61')
+
+  return sqliteParser(fixedSql)
+}
+
+/*
+ * Return an array of columns with name and type. E.g.:
+ * [
+ *   { name: 'id',    type: 'INTEGER' },
+ *   { name: 'title', type: 'NVARCHAR(30)' },
+ * ]
+*/
+function getColumns (sql) {
+  const columns = []
+  const ast = getAst(sql)
+
+  const columnDefinition = ast.statement[0].format === 'table'
+    ? ast.statement[0].definition
+    : ast.statement[0].result.args.expression // virtual table
+
+  columnDefinition.forEach(item => {
+    if (item.variant === 'column' && ['identifier', 'definition'].includes(item.type)) {
+      let type = item.datatype ? item.datatype.variant : 'N/A'
+      if (item.datatype && item.datatype.args) {
+        type = type + '(' + item.datatype.args.expression[0].value
+        if (item.datatype.args.expression.length === 2) {
+          type = type + ', ' + item.datatype.args.expression[1].value
+        }
+        type = type + ')'
+      }
+      columns.push({ name: item.name, type: type })
+    }
+  })
+  return columns
+}