WebAssembly.Table()

WebAssembly.Table() 构造函数根据给定的大小和元素类型创建一个Table对象。 

这是一个包装了WebAssemble Table 的Javascript包装对象，具有类数组结构，存储了多个函数引用。在Javascript或者WebAssemble中创建Table 对象可以同时被Javascript或WebAssemble 访问和更改。

Syntax

var myTable = new WebAssembly.Table(tableDescriptor);

Parameters

tableDescriptor

该对象具有以下属性：

element

一个表明储存在该Table中对象的类型。 目前只能是：  "anyfunc" (函数)。

initial

该WebAssembly Table初始大小。

maximum 可选

该WebAssembly Table允许扩展到的最大大小。

Exceptions

• 如果 tableDescriptor 不是对象类型, 将会抛出 TypeError 异常。
• 如果申明了 maximum 属性并且比 initial小, 将会抛出RangeError 异常。

Table instances

All Table instances inherit from the Table() constructor's prototype object — this can be modified to affect all Table instances.

Instance properties

Table.prototype.constructor

Returns the function that created this object's instance. By default this is the WebAssembly.Table() constructor.

Table.prototype.length

Returns the length of the table, i.e. the number of elements.

Instance methods

Table.prototype.get()

Accessor function — gets the element stored at a given index.

Table.prototype.grow()

Increases the size of the Table instance by a specified number of elements.

Table.prototype.set()

Sets an element stored at a given index to a given value.

Examples

The following example (see table2.html source code and live version) creates a new WebAssembly Table instance with an initial size of 2 elements. We then print out the table length and contents of the two indexes (retrieved via null.

var tbl = new WebAssembly.Table({initial:2, element:"anyfunc"});
console.log(tbl.length);  // "2"
console.log(tbl.get(0));  // "null"
console.log(tbl.get(1));  // "null"

We then create an import object that contains the table:

var importObj = {
  js: {
    tbl:tbl
  }
};

Finally, we load and instantiate a wasm module (table2.wasm) using the WebAssembly.instantiateStreaming() method.  The table2.wasm module contains two functions (one that returns 42 and another that returns 83) and stores both into elements 0 and 1 of the imported table (see text representation).  So after instantiation, the table still has length 2, but the elements now contain callable Exported WebAssembly Functions which we can call from JS.

WebAssembly.instantiateStreaming(fetch('table2.wasm'), importObject)
.then(function(obj) {
  console.log(tbl.length);
  console.log(tbl.get(0)());
  console.log(tbl.get(1)());
});

Note how you've got to include a second function invocation operator at the end of the accessor to actually invoke the referenced function and log the value stored inside it (e.g. get(0)() rather than get(0)) .

This example shows that we're creating and accessing the table from JavaScript, but the same table is visible and callable inside the wasm instance too.

Specifications

Browser compatibility

See also

• WebAssembly overview page
• WebAssembly concepts
• Using the WebAssembly JavaScript API